The Best S'mores Cake

5 from 1 vote

We've made a campfire treat into a showstopping s’mores cake. Layers of rich chocolate sponge, toasted marshmallow frosting, and crunchy biscuit crumbs come together for a chocolatey delight.

Prep Time1

Cook Time30

Total Time1 30

Course: Baking

Cuisine: American

Servings: servings

Ingredients

For the sponge:

200 g dark chocolate
150 g unsalted butter softened
90 g vegetable oil
300 g caster sugar
3 large eggs
40 g unsweetened dark cocoa powder
225 g self-raising flour
350 ml boiling water
10 g instant coffee granules

For the ganache

600 g dark chocolate
300 ml double cream
Pinch of salt

For the biscuit crumb:

120 g lotus biscuits
40 g butter

For the marshmallow frosting:

300 g caster sugar
160 g egg whites

To decorate

Marshmallows as many as you like

Instructions

For the biscuit crumb:

Blitz the lotus biscuits in a food processor (or bash in a sealed sandwich bag). Transfer to a bowl and mix in the melted butter.

To make the cake:

Heat the oven to 170C fan/190c conventional/375f. Line 3 x 18cm cake tins with parchment.
Melt the chocolate over a Bain Marie and leave to the side to cool.
In a stand mixer, beat the softened butter and caster sugar together for 2 minutes until smooth and pale. Add the eggs, mixing in each one before adding the next.
Then pour in the melted chocolate and mix briefly to combine. Drizzle in the oil while mixing.
Add the flour, cocoa powder and pinch of salt. Mix well.
In a jug, mix 350ml boiling water with the instant coffee granules. Pour slowly into the bowl of cake batter, mixing until the batter is smooth. It will look thin – that’s normal.
Divide the mixture between the cake tins and bake for 25-30 minutes or until a skewer comes out clean when inserted.

To make the ganache:

Finely chop the chocolate. Gently heat the double cream in a saucepan. Keep an eye on it as it can boil over easily.
Add the chocolate to a large, heatproof bowl and once the cream is simmering, pour it over the chocolate. Add a pinch of salt and give it a minute to melt slightly before using a whisk to mix everything together until smooth.
If you find the ganache has some small lumps of chocolate that won’t melt, you can gently heat over a Bain Marie whilst whisking to help things along. Set aside to cool or pop in the fridge to firm up slightly - don’t leave it too long as it can harden very quickly!

For the marshmallow frosting:

Place sugar and egg whites into a heatproof bowl and place over a saucepan of barely simmering water.
With a manual whisk, whisk until all the sugar is dissolved and you can no longer see or feel any small grains of sugar. To test this, rub a little of the mixture (it should be gently warm and not hot) between your forefinger and thumb. It should feel totally smooth. It will still look very loose; you aren’t whisking until thick.
Once the sugar is dissolved, place this mixture into the bowl of a stand mixer and whisk until you get a thick and stiff meringue, about 10 minutes. If you don’t have a stand mixer, a handheld electric whisk will work.
If you like, I find it easiest to transfer to a piping bag (or sandwich bag with the corner cut off). Otherwise, leave in the bowl and set aside until ready to assemble.

To assemble the cake:

Place one sponge on a serving plate or cake stand.
Spread a thick layer of ganache over the top. Top with biscuit crumbs and then pipe/spread on the marshmallow frosting. Top with the second sponge.
Cover the entire cake with the remaining ganache, smoothing the sides with a palette knife or spatula. Then swipe on little patches of the marshmallow frosting and sprinkle crumbs around the base of the cake. Top with marshmallows, mine were homemade but shop-bought is of course fine.
Use a blowtorch to lightly brown the marshmallow frosting and the marshmallows for a golden toasted s'mores look.

Notes

Scroll up for a step by step guide on how to make s'mores cake.

To store: The assembled cake will keep in an airtight container at room temperature for 2 days or in the fridge for up to 3 days. If refrigerated, remove the cake from the fridge 20 mins before serving so it loses the fridge chill (unless it’s a super hot day as you don’t want it to melt).

To freeze: The unfrosted sponge layers freeze well. Wrap each layer individually in baking parchment, then cling film, and freeze for up to 3 months. Defrost overnight at room temperature before frosting. I like to make the ganache fresh for best results but it does keep in the fridge for a few days. Just bring it to room temperature before trying to spread it.

Make ahead: The sponge layers can be baked 1–2 days ahead. Once cooled, wrap tightly in baking parchment and cling film, then store at room temperature until ready to assemble.

The ganache can also be made in advance. Keep in the fridge for up to 48 hours, then bring back to room temperature and mix to bring together before spreading. Biscuit crumbs keep in the fridge for 3 days too.

Make the marshmallow frosting when needed so it keeps its airiness.

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