S’mores Cake!

A rich chocolate sponge layered with marshmallow fluff buttercream, topped with toasted marshmallows, biscuit crunch, and a glossy chocolate drip. This recipe makes a 3-layer 8-inch cake (around 14–16 slices), takes about 50 minutes of active prep, and is straightforward once the structure is understood.

This is a high-impact celebration cake that looks bakery-level but is built on simple, reliable techniques.

Notes from The Patisserie

I’ve been wanting to make a S’mores Cake for a good while now, but I knew I should wait till Autumn and Halloween/Guy Fawkes time to post it. Bonfire Night is great, and I always make an awkward UK version of S’mores with digestives, but it’s still damn delicious.

What can you not like about marshmallow, chocolate and biscuits all smooshy and melted together? YUMMY. Like seriously, it’s not necessarily for the people who don’t like very sweet things, but it is oh so delicious.

The most common issue with S’mores layer cakes is structural instability, particularly slippage between sponge layers. This usually happens when the buttercream is too soft or the cake layers are still slightly warm when assembled.

I find the other frequent problem is buttercream becoming loose due to over-mixing the marshmallow fluff. While fluff adds sweetness and texture, too much agitation can break down the structure and make it harder to use for clean layering.

Ingredients and tips

I’ve picked these ingredients specifically to make sure the cake stays standing and tastes amazing.

• Butter – For this sort of bake, you can use block butter or a baking spread. In the sponge, it builds a firmer crumb that can physically support stacking, while in the buttercream it stabilises the marshmallow fluff so the layers hold their shape when chilled or sliced.
• Sugar – I went for all light brown sugar as I like the flavour, but you can swap all or part for white granulated sugar like in my other cake bakes. The moisture content also helps the sponge stay soft under heavy frosting and prevents it drying out once assembled.
• Flour – Ideally, you need self-raising flour as we are going to supplement with baking powder for extra lift – you can use 325g of plain flour with 4.5 tsp of baking powder if not (in addition to the extra baking powder).
• Raising agents – essential for providing the extra lift and counteracting the heaviness of the cocoa.
• Icing sugar – Sift to avoid clumps and ensure a smooth finish, a good quality icing sugar will avoid the clouds as you measure out.
• Marshmallow fluff – I found tubs of this for sale in most UK supermarkets and it is readily available in the US.
• Vanilla – I use vanilla in most of my chocolate bakes as it enhances the flavour that is particularly true with the “toasted” flavour of the finished S’mores Cake.
• Chocolate – I use a good quality 70% dark chocolate for the drip as it sets more firmly than milk chocolate. You can use milk chocolate but reduce the oil content to avoid overly runny drips.
• Oil – Sunflower or vegetable oil creates the glossy shine in the drip and won’t create snaps when slicing the cake.
• Biscuits – Any crushed biscuits or small pieces work best for texture contrast on top. Smaller pieces prevent the topping sliding off the buttercream and help it sit more evenly across the semi-naked finish.
• Marshmallows – Large works work best for toasting as you can crisp the edges and leave the soft chewy centres.

Making the best drip cake

To achieve those clean layers and perfect, beaded drips, you have to treat the assembly as a game of patience rather than a race. The process starts with the bake itself, you can actually tell the cake is cooked because when it is not done, it will make a subtle bubbling or crackling sound. Once that sound has stopped and the sponge springs back, you know it’s ready.

You should never, ever frost a sponge that is even slightly warm, so for a S’mores cake specifically, I actually recommend making your sponges a day ahead, wrapping them tightly, and chilling them. Cold sponges are much firmer and easier to stack, which is vital when you are working with a softer frosting like marshmallow fluff buttercream. If you want to make it extra “S’moresy,” you can even scatter some mini marshmallows and crushed biscuits between the layers as you stack them for a little hidden texture.

Once you start stacking, the most important step is the crumb coat. This is your “primer” layer a very thin coating of buttercream that locks in the crumbs and fills any gaps between your layers. After applying this, you must chill the cake for at least 30 minutes to create a rock-solid foundation for your final finish.

If you do want that sharp, bakery-style finish, I seriously recommend using a metal scraper and disposable piping bags. When you finally go to apply the chocolate drip, the temperature contrast is your best friend. Your cake should be fridge-cold, but your chocolate should be roughly body temperature. When that warm chocolate hits the cold buttercream, it slows down naturally, allowing you to control exactly how far it travels down the side of the cake.

Making a smaller cake

I realise that this cake is quite larger, so you may want to make a smaller version of it, but still get that delicious taste.

• To make a smaller version of the cake, use:
  • Two 8″cake tins
  • 300g Butter
  • 300g Sugar
  • 245g Flour
  • 55g Cocoa Powder
  • 1.5tsps baking powder
  • It might take an extra 5-10 minutes to bake
  • Use 2/3 of the decoration recipes

FAQs

Storage and freezing

This cake will keep in the fridge for up to 3 days in an airtight container. The sponge remains moist, although the biscuit topping will soften slightly over time.

You can freeze the sponge layers before assembly for up to 3 months. Once fully assembled, freezing is not recommended due to the marshmallow buttercream structure.

Related Recipes

If you enjoy this S’mores cake, you’ll likely enjoy other indulgent layered and chocolate-based bakes. My Oreo drip cake offers a similar structure with a cookies-and-cream twist, while the Rolo cookie bars bring a softer, fudgier chocolate caramel option. For a more classic bake, a simple chocolate fudge cake delivers the same richness in a more traditional format.