This is a gluten-free chocolate cake with a thick dark chocolate mousse layer on top — two components, one springform tin, and a result that holds up well enough to serve at a dinner party. The cake base uses sour cream and oil instead of butter, which keeps it moist even after a night in the fridge. If you’re baking for someone with coeliac disease, or you just want a chocolate dessert that actually sets properly and slices cleanly, this one delivers.
The short version of why this works
Two things matter here. First, the sour cream and oil combination in the cake batter — oil coats the flour proteins without building structure the way butter does, and sour cream adds moisture plus a little acidity that keeps the crumb tender. This is especially important with gluten-free flour, which can turn dense and gummy if the fat ratio is off. Second, the mousse sets through cold temperature alone, not gelatine. That only works if the whipped cream reaches stiff peaks before you fold in the chocolate mixture — soft peaks will give you a mousse that stays loose and never fully firms up. Get those two things right and the rest is straightforward.
Smart swaps
- Gluten-free flour blend: Any plain gluten-free all-purpose blend works here. Check the bag — if xanthan gum is already listed in the ingredients, skip the additional teaspoon the recipe calls for. Adding extra will make the cake gummy.
- Sour cream: Full-fat plain Greek yogurt is a direct swap, same quantity. Don’t use low-fat — the reduced fat content affects the texture of the crumb.
- Dark chocolate for the mousse: Anything between 50% and 70% cocoa solids works. Below 50% the mousse can be too sweet and may not set as firmly. Above 70% it can turn slightly grainy when folded into cream.
- Thickened cream (heavy cream): This needs to be at least 35% fat to whip to stiff peaks. Half-and-half or light cream won’t work — the mousse won’t set.
- Icing sugar in the mousse: Regular granulated sugar won’t dissolve properly into cold whipped cream. Stick with powdered sugar, or blitz granulated sugar in a blender for 30 seconds first.
Leftovers and make-ahead
This cake is genuinely better after an overnight rest in the fridge — the mousse firms up completely and the flavours settle. You can make it up to two days ahead; keep it covered in the springform tin until you’re ready to serve. After slicing, store leftovers covered in the fridge for up to three days. The mousse layer will hold its texture well. For longer storage, individual slices freeze well — wrap each one tightly in plastic wrap and freeze for up to six weeks. Thaw overnight in the fridge, not at room temperature, so the mousse doesn’t weep.
Common problems and fixes
- The cake sinks in the middle after baking: This usually means it came out of the oven too early. The toothpick test is the reliable check — a few moist crumbs are fine, but wet batter means it needs more time. Gluten-free cakes can look done on top while the centre is still underbaked.
- The mousse won’t set after 4 hours: The cream was likely under-whipped before folding. If this happens, don’t panic — return the whole tin to the freezer for 45 minutes, then move it back to the fridge. It will firm up enough to slice cleanly.
- The mousse looks streaky or lumpy after folding: The melted chocolate was still too warm when added to the cream, which causes it to seize into small lumps. Let the chocolate mixture cool until it’s just barely warm to the touch — not hot — before folding.
- The cake crumbles when you try to trim it to fit the springform tin: Gluten-free cake is more fragile than wheat-based cake, especially at the edges. Chill the cake in the fridge for 20 minutes before trimming — it firms up enough to handle without breaking apart. Skip the garnish — not worth the extra dish when a clean slice speaks for itself.
- The collar tears when you peel it away: Grease the baking paper strip well before pressing it against the inside of the tin. If it still sticks, use a thin palette knife or butter knife to gently separate it from the mousse before peeling.
Guilt-Free Chocolate Mousse Cake (Gluten-Free)
Ingredients
For the cake
- 1 ¼ cups gluten-free plain flour (all-purpose)
- 1 teaspoon xanthan gum omit if blend contains it
- 10 tablespoons unsweetened cocoa powder
- 0.4 teaspoon salt
- 0.4 teaspoon baking soda
- ¾ cup caster sugar granulated sugar
- ½ cup sour cream at room temperature
- 6 ⅓ tablespoon vegetable oil
- 1 large egg beaten, room temperature
- 1 large egg yolk room temperature
- ½ cup warm water
- 1 tablespoon warm water additional
For the chocolate mousse
- 3 tablespoons unsweetened cocoa powder
- ½ cup warm water
- 1 tablespoon warm water additional
- 10 ounces dark chocolate 50–70% cocoa solids, chopped
- 4 tablespoons unsalted butter chopped
- 2 cups thickened cream cold
- ¼ cup icing sugar powdered sugar
Instructions
- Preheat the oven to 180°C / 350°F (160°C fan-forced). Grease and line an 8-inch (20cm) round cake tin with baking paper.
- To make the cake, place the gluten-free flour, xanthan gum, cocoa powder, salt, baking soda, and sugar in a large bowl. Whisk to combine.
- Create a well in the centre of the dry ingredients. Add the sour cream, vegetable oil, beaten egg, egg yolk, and 1/2 cup (120ml) warm water, mixing well after each addition. The batter will be thick.
- Pour the batter into the cake tin and smooth it out.
- Bake for 25-30 minutes or until a toothpick or skewer inserted into the centre comes out with just a few moist crumbs attached. Leave the cake to cool completely in the tin while you prepare the mousse.
- For the mousse: whisk the 20g cocoa powder with 1/2 cup (120ml) warm water and the additional 1 tablespoon of warm water in a small bowl until completely dissolved and smooth. Set aside. Melt the butter and chopped dark chocolate in a microwave-safe bowl in 30-second bursts, stirring between each, until fully melted and smooth. Set aside to cool to room temperature.
- In a stand mixer fitted with the whisk attachment (or using a hand mixer), whip the cold cream on medium speed until soft peaks form. Add the icing sugar gradually, then increase speed to medium-high and whip until thick, glossy, and holding stiff peaks.
- Add the cocoa mixture to the melted chocolate mixture. Gently fold the chocolate mixture into the whipped cream until fully combined.
- To assemble, place the cooled chocolate cake into the base of an 8-inch (20cm) or 9-inch (23cm) springform tin with tall sides. Trim edges if needed to fit. Secure a cake collar or greased baking paper strip around the inside edge of the tin.
- Pour the chocolate mousse over the cake and smooth the top. Refrigerate for at least 4 hours, or ideally overnight, until fully set.
- Carefully remove the springform ring and peel away the collar. Garnish with fresh raspberries, cocoa powder, or chocolate shavings. Serve cold.
Nutrition
Frequently asked questions
Can I use a regular (non-springform) cake tin for the whole thing?
No — you need a springform tin for the assembled cake. The mousse layer has to be poured over the cake and set in the tin, and you can’t unmould it cleanly without the removable sides. A regular tin works fine for baking the cake base itself, but you’ll need to transfer it to a springform tin before adding the mousse.
What if I don’t have a stand mixer or hand mixer for the cream?
You can whip cream by hand with a balloon whisk, but it takes 8 to 12 minutes of steady whisking and the bowl and cream both need to be very cold. Put the bowl in the freezer for 10 minutes before you start. It’s tiring but it works.
Can I use milk chocolate instead of dark chocolate in the mousse?
You can, but the mousse will be noticeably sweeter and may set slightly softer because milk chocolate has a higher sugar and milk-solid content and less cocoa butter. If you go that route, reduce the icing sugar in the mousse by half to balance it out.
Does this need to be served the same day, or can I make it the night before a party?
Make it the night before — it actually sets better and slices more cleanly after a full overnight chill. Just leave it in the springform tin, covered with plastic wrap, and unmould it right before serving.
If you liked this one
- Dark Chocolate Mousse
- Chocolate Brownies
- Giant Chocolate Chip Cookie Cake
- Strawberry Cake with Whipped Cream
