Keto Chocolate Graveyard Sheet Cake with Sugar-Free Mousse (Halloween Showstopper)

You know that one dessert everyone crowds around at the Halloween party?

The one folks pretend to be scared of, but they keep sneaking back for another forkful?

That can be your cake this year. This keto chocolate graveyard sheet cake is rich, moist, and topped with a fluffy sugar-free mousse that tastes like a chocolate cloud.

 Then we pile on spooky “dirt,” tombstones, bones, and a web that looks straight out of a haunted movie set. It’s bold without being fussy, and it plays nice with low-carb goals.

I first baked this for a neighborhood party where half the group was watching carbs and the other half just wanted chocolate.

The pan came back clean. Someone even asked if I cheated with real sugar. Nope. The trick is simple ingredients, the right sweetener combo, and a few Halloween touches that make people grin.

Below you’ll find everything you need: ingredients with easy swaps, step-by-step instructions, make-ahead tips, and ideas to decorate fast or go all out.

Simple language, straight talk, and lots of tiny details so you nail it on the first try.

What Makes This Cake Yummy (and still keto)

• Moist crumb without wheat flour: Almond flour gives body. A small spoon of coconut flour balances moisture so the cake slices cleanly.
• Deep chocolate taste: Cocoa powder plus a touch of coffee wakes up the chocolate. You will not taste coffee in the final cake.
• Sweet but not icy: A blend of allulose and erythritol keeps sweetness pleasant. Allulose stops that cold, minty feel some sweeteners have.
• Light mousse topping: Whipped cream and cream cheese make a stable, sugar-free chocolate mousse that holds shape on a sheet cake.
• Easy decoration base: A pan of cake means lots of real estate for a graveyard scene. No piping skills needed.

Tools You’ll Need

• 9 x 13 inch metal baking pan (or similar casserole dish)
• Parchment paper
• Two mixing bowls (one large, one medium)
• Hand mixer or stand mixer
• Whisk and rubber spatula
• Measuring cups and spoons
• Small microwave-safe bowl for melting chocolate
• Offset spatula for frosting (a butter knife works in a pinch)
• Fine mesh sieve (for smoothing cocoa and sweetener lumps)
• Optional: Piping bag or zip bag for the spider web and RIP letters

Ingredients

For the Keto Chocolate Sheet Cake

• 2 cups (200 g) almond flour, super-fine
• 2 tbsp coconut flour
• ¾ cup (75 g) unsweetened cocoa powder
• 1 tbsp baking powder
• ½ tsp baking soda
• ½ tsp fine salt
• ½ cup allulose
• ½ cup granulated erythritol (or monk fruit erythritol blend)
• 4 large eggs, room temp
• ½ cup avocado oil (or light olive oil)
• ¾ cup unsweetened almond milk (or any low-carb milk)
• 2 tsp vanilla extract
• 1 tsp instant coffee or ½ cup hot brewed coffee in place of part of the milk (optional, for flavor)
• 2 tbsp sour cream (adds moisture and helps with crumb)

For the Sugar-Free Chocolate Mousse Topping

• 8 oz (225 g) cream cheese, room temp
• 1 cup heavy whipping cream, very cold
• ¼ cup powdered allulose
• ¼ cup powdered erythritol (or just allulose if you prefer)
• ¼ cup unsweetened cocoa powder
• 1 tsp vanilla extract
• Pinch of salt

For the Graveyard Decorations (pick a few or go wild)

• Dirt: 1 to 1½ cups crushed keto chocolate cookies or brownies dried and crumbled, or shaved sugar-free chocolate
• Tombstones: Sugar-free chocolate bars broken into rectangles, or keto shortbread cookies cut into headstone shapes
• RIP letters: Melted sugar-free white chocolate or a quick sugar-free icing (2 tbsp powdered sweetener + drops of water)
• Bones: Sliced almonds arranged like tiny bones, or sugar-free meringue bones if you want to make them
• Ghosts: Unsweetened whipped cream dollops with sugar-free chocolate chips for eyes
• Pumpkin patch look: Sugar-free orange candies or small strawberries dipped in tinted sugar-free white chocolate
• Spider web: Melted sugar-free dark chocolate and a little melted sugar-free white chocolate

Making the Best Keto Chocolate graveyard sheet cake with sugar-free mousse

Step-By-Step: The Cake

• Heat the oven: Set to 350°F (175°C). Line your 9 x 13 pan with parchment, leaving a little overhang to lift later. Lightly spray or oil the sides.
• Mix dry ingredients: In a large bowl whisk almond flour, coconut flour, cocoa powder (sift if clumpy), baking powder, baking soda, salt, allulose, and erythritol. This even mix is your insurance for a nice crumb.
• Mix wet ingredients: In a medium bowl whisk eggs until a little foamy. Add oil, almond milk, vanilla, sour cream, and instant coffee if using. Whisk till smooth.
• Combine: Pour wet into dry. Switch to a spatula and fold until you see no dry pockets. Batter will be thick but spreadable. If it feels stiff like brownie batter, add 1 to 2 tbsp almond milk.
• Bake: Spread batter in the pan, smooth the top. Bake 22 to 28 minutes, till the center springs back lightly and a toothpick comes out with a few moist crumbs. Do not overbake; dry cake is scarier than any ghost.
• Cool: Let cool in the pan on a rack at least 45 minutes. The mousse goes on a cool cake only.

Make the Sugar-Free Chocolate Mousse

• Whip the cream: In a cold bowl, whip heavy cream to medium-stiff peaks. Don’t push it to butter. Set aside.
• Cream the base: In another bowl, beat cream cheese with powdered allulose and erythritol until smooth and fluffy. Add cocoa powder, vanilla, and a pinch of salt. Beat again till silky and no lumps.
• Lighten it: Fold one third of the whipped cream into the chocolate base to loosen. Fold in the rest gently until no streaks remain. You want a light, airy mousse.

Frost and Build the Graveyard

• Mousse layer: Spread the mousse over the cool cake. Use an offset spatula to make soft waves. Chill 15 minutes to set the surface.
• Add dirt: Sprinkle crushed keto cookies or shaved chocolate over parts of the cake, leaving some mousse showing so there’s contrast. Think patches of soil, not a flat field.
• Place tombstones: Press chocolate bar rectangles or cookie headstones upright into the “dirt.” If your kitchen is warm, chill the tombstones a few minutes first so they stand firm.
• RIP letters: Pipe “RIP,” skulls, tiny crosses, or names on the tombstones with melted sugar-free white chocolate or quick icing. If writing looks wonky, call it haunted calligraphy and move on. It still reads spooky.
• Bones and ghosts: Scatter sliced almonds like bones, or drop small whipped cream ghosts and add two tiny chocolate chips for eyes.
• Spider web: Drizzle thin circles of dark chocolate across an open mousse area. While still soft, drag a toothpick outward from the center at intervals to form a web. Add a little white chocolate spider if you feel brave.

Texture and Taste Notes

• The cake itself is rich and tender. It does not crumble apart like some low-carb cakes, thanks to the split of almond and coconut flour.
• The mousse is gently sweet and chocolatey, not heavy. It holds well on the cake without sliding off.
• Decorations bring crunch and contrast. You get spoonfuls of mousse, a soft bite of cake, and the snappy crack of a chocolate tombstone. That mix makes people take another slice.

Ingredient Swaps and Tips

• Sweeteners: If you only have one sweetener, use powdered allulose throughout. If using only erythritol, sweetness is fine, but you may feel a little cool aftertaste. Mixing the two reduces that.
• Dairy-free: Swap heavy cream for coconut cream and cream cheese for a vegan cream cheese that is low carb. The taste will shift slightly but still good.
• Egg-free: This cake leans on eggs for structure. If you must, try a chia egg (1 tbsp chia + 2½ tbsp water, rested) per egg, but texture will be denser.
• Oil vs butter: Oil keeps the crumb moist. Melted butter works but cools a bit firmer.
• Coffee: Tiny dose wakes up cocoa. If serving kids and you want none, skip it. No big loss.
• Almond allergy: Use fine sunflower seed flour for a similar texture. Add a teaspoon of lemon juice to counter green tint that sometimes shows with sunflower and baking soda.

What to do

• Cake sunk in the center: Usually from underbaking or old baking powder. Bake until the middle springs back. Check your leaveners’ dates.
• Grainy mousse: Cream cheese was not soft enough. Beat it longer to smooth before adding whipped cream. If already grainy, warm the bowl slightly over hot water and whisk carefully.
• Bitter chocolate taste: Some cocoa powders are strong. Add 1 to 2 tbsp extra powdered sweetener to the mousse, or a drop or two of vanilla.
• Tombstones won’t stand: Make a thicker “dirt” mound. Press tombstones in at a slight angle. Chill 10 minutes to set.

Step-By-Step Timeline (so you stay sane)

• Day before (optional): Bake the cake. Wrap and chill.
• Party day, 1½ hours before serving: Make mousse, frost cake, chill 15 minutes.
• 1 hour before: Add dirt and tombstones. Pipe letters. Chill again.
• 30 minutes before: Add ghosts and spider web. Keep chilled till serving.

Make-Ahead, Storage, and Freezing

• Make-ahead: Cake base keeps well wrapped in the fridge up to 3 days. Mousse can be made the day you serve for best texture, but it also holds 24 hours.
• Leftovers: Cover and chill up to 4 days. The “dirt” softens a bit but the taste stays lovely.
• Freezing: Freeze the cake base alone up to 2 months. Thaw in the fridge overnight. I do not freeze the mousse-topped version; texture is better fresh.

How to Cut Clean Slices

• Use a long, sharp knife. Wipe the blade with a warm damp cloth between cuts.
• Slice through the tombstones first and set them aside. Then cut the cake into neat rectangles. Put the tombstones back if you like drama on plates.

Simple Version (for busy nights)

Short on time? Do this:

• Bake the cake as written.
• Frost with lightly sweetened whipped cream (skip the cream cheese and cocoa for a pale ghostly topping).
• Dust with cocoa and add a few chocolate bar tombstones with quick “RIP” letters. Done. Still cute, still tasty.

Fancy Version (for the show-off in all of us)

• Pipe little meringue bones with a sugar-free meringue and dry them in a low oven.
• Add sugar-free candy pumpkins and chocolate trees drawn on parchment, chilled till firm.
• Make a white chocolate moon and a bat or two. You can cut shapes from a flat slab of melted sugar-free chocolate.

Nutrition (estimate, because ingredients vary)

Assuming 16 slices and decorations kept moderate:

• Calories: ~275 per slice
• Fat: ~24 g
• Net Carbs: ~4 to 5 g (depends on sweeteners and cookie “dirt”)
• Protein: ~7 g

To keep carbs low, use shaved chocolate for dirt instead of cookies, or bake a single thin keto brownie just to crumble.

Why Many Loves This One

• It looks like a bakery cake but comes together with pantry basics.
• It holds up well on a buffet. The mousse doesn’t melt off in 20 minutes.
• You can tweak the graveyard scene for any crowd. Cute or creepy. Minimal or extra. Kids can help and no one cries if a tombstone tilts.

Flavor Boosters You Can Add

• Orange twist: Add ½ tsp orange extract to the mousse and zest of half an orange to the cake batter. Orange and chocolate never fight.
• Peppermint night: Add ¼ tsp peppermint extract to the mousse for a cold-night vibe. Nice if you skip the coffee.
• Cinnamon cocoa: A pinch of cinnamon in the cake plus a dusting on top plays up warmth.

Clean Keto Tips (so you feel good after dessert)

• Choose cocoa powder with no added sugar. Obvious, but labels get tricky.
• If your cookies for dirt list wheat flour, carbs jump fast. Better to crush a small square of your favorite keto brownie or grate a sugar-free chocolate bar.
• Keep portions reasonable. This cake is rich and satisfying, so smaller squares do the trick.

Decorating Map (quick layout plan)

• Top left corner: Big spider web.
• Top right: Three tombstones, one cracked, one tilted, one with a silly name like “Ben Better.”
• Bottom left: Patch of dirt with bone scatter.
• Bottom right: Two whipped cream ghosts guarding the path.

Divide your cake into four zones in your mind and you’ll decorate faster with balance. If symmetry gives you comfort, mirror the corners.

Party Game Add-On

Set out a small bowl of “graveyard gravel” (sugar-free chocolate chips and chopped nuts) so guests can sprinkle extra crunch on slices. Kids love the control, and it keeps little hands out of the main cake.

Cost and Pantry Notes

• Almond flour and cocoa are the main cost. Buy almond flour in larger bags and keep it sealed in the fridge for freshness.
• Allulose can be pricier than erythritol, but even a small portion of allulose in the blend improves texture. If budget is tight, do three parts erythritol to one part allulose.
• Use store brand almond milk. It’s fine here.

Personal Notes From My Kitchen

• I keep a small jar of “cake rescue” mix: 2 tbsp powdered allulose, 1 tbsp cocoa, tiny pinch of salt. If a frosting tastes flat, a shake of this fixes it fast.
• On a hot day, I freeze the chocolate tombstones on a little tray for 10 minutes. They stand tall and do not slump.
• I once wrote “RIP Carbs” on the center stone. Even the non-keto folks laughed, then asked for seconds.

Serving Ideas

• Serve plain or with a spoon of lightly sweetened whipped cream on the side.
• Add fresh raspberries for a pop of color and tart edge that cuts through the chocolate.
• For grown-ups, a small espresso beside this cake is chef’s kiss.

Clean-Up Tips

• Soak the mixer beaters and bowl right after whipping cream. Dried cream sticks like cement.
• Line the counter with parchment when you drizzle the web. Then you crumple it up and toss. No chocolate splatter on tiles.
• Parchment sling in the pan makes lifting easy. Peel it down, cut neat slices, done.

Conclusion

You don’t need pastry school moves to make a Halloween cake that stops the room. Stick to the steps, aim for good flavor first, and let the decorations be loose and playful. A crooked tombstone looks more like a real graveyard anyway. The cake tastes rich, the mousse stays light, and your low-carb plan stays intact. If your party runs late, the leftovers tomorrow are even better after a night in the fridge.

Now go preheat that oven. The ghosts are waiting.

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