Devils Food Mousse Cake

A rich, moist Devil's food cake that's genuinely low in sugar, filled with a light chocolate mousse rather than a dense ganache, finished with a thin ganache drip. Dark chocolate flavour throughout, but not bitter.

> Naturally gluten-free sponge, made with Freee plain gluten-free flour, goat buttermilk (or goat milk) and rapeseed oil, with real sugar kept deliberately low and topped up with monk fruit sweetener.

Ingredients

Sponge

• 200g Freee plain gluten-free flour
• 50g unsweetened cocoa powder
• 60g dark brown sugar
• 40g Groovy Keto 1:1 monk fruit sweetener
• 2 tsp baking powder
• ⅔ tsp bicarbonate of soda
• ⅓ tsp fine salt
• 4 medium eggs, room temperature
• 60g rapeseed oil
• 160ml goat buttermilk, or 155ml goat milk + 5ml lemon juice, left 10 minutes
• 120ml strong hot decaf coffee
• 1⅓ tsp vanilla

Light chocolate mousse filling

• 300ml Longley Farm whipping cream, very cold
• 90g dark chocolate total: 45g 75%, 45g Green & Black's 85%
• 8g cocoa powder
• 22g hot water
• 2 medium egg whites
• ¾ tsp vanilla
• small pinch salt
• No added sugar

Ganache drip

• 100g dark chocolate total: 50g 75%, 50g Green & Black's 85%
• 125ml Longley Farm whipping cream
• No added sugar

Method

1. Bake the sponge

1. Heat oven to 170°C conventional / 150°C fan.

2. Grease and base-line 3 × 7-inch tins.

3. Mix the 50g cocoa with the 120ml hot coffee until smooth. Leave to cool until just warm.

4. Sift together the flour, baking powder, bicarbonate and salt.

5. Whisk the 4 eggs, brown sugar and monk fruit for about 4–5 minutes until noticeably paler, thicker and aerated.

6. With the mixer on low, slowly drizzle in the rapeseed oil.

7. Mix in the vanilla.

8. Fold in, in this order: ⅓ dry ingredients, ½ buttermilk, ⅓ dry ingredients, remaining buttermilk, remaining dry ingredients.

9. Fold through the cooled cocoa-coffee mixture gently.

10. Divide evenly between the three tins.

11. Bake for about 20–25 minutes. Check from 20 minutes — a skewer should come out with a few moist crumbs, not wet batter.

12. Cool in tins for 10 minutes, then turn onto racks and cool completely.

2. Make the mousse

1. Mix the 8g cocoa with the 22g hot water until completely smooth.

2. Melt the 90g chocolate gently.

3. Stir the cocoa mixture into the melted chocolate.

4. Leave until room temperature but still fluid.

5. Whip the 300ml cream with the vanilla to medium-firm peaks.

6. In a separate clean bowl, whisk the 2 egg whites with the pinch of salt to soft-medium peaks.

7. Fold about ¼ of the whipped cream into the chocolate mixture to loosen it.

8. Fold in the remaining whipped cream gently.

9. Fold in the whipped egg whites in 2 additions.

10. Chill for about 30 minutes, until fluffy but firm enough to spread.

3. Assemble

1. Put the first sponge layer on the serving plate.

2. Spread over half the mousse, leaving about 1cm clear around the edge.

3. Add the second sponge.

4. Spread over the remaining mousse.

5. Add the final sponge.

6. Press very gently — do not compress the mousse.

7. Chill the assembled cake for at least 1 hour before adding ganache.

4. Make the ganache drip

1. Finely chop the 100g chocolate.

2. Heat the 125ml whipping cream until steaming but not boiling.

3. Pour over the chocolate.

4. Leave for 2 minutes.

5. Stir gently from the centre until smooth and glossy.

6. Leave to cool until barely warm and still fluid.

7. Test one drip down the side of the chilled cake: if it runs straight to the plate it's too warm; if it barely moves it's too cool/thick.

8. Once right, spoon drips around the edge.

9. Spread a thin layer over the top.

Notes

• Cake style: rich, moist Devil's food rather than a very light fatless sponge.
• Tins: 3 × 7-inch round tins.
• Flour: use Freee plain gluten-free flour, not self-raising, so the raising agents are controlled separately.
• Sugar: deliberately very low. 60g dark brown sugar gives moisture, flavour and structure; 40g 1:1 monk fruit keeps sweetness low without stripping out all the real sugar. Emma would not reduce the real sugar further on the first bake.
• Cocoa: bloom it in the hot coffee for a deeper chocolate flavour without needing melted chocolate in the sponge.
• Coffee: use strong decaf — it should deepen the cocoa rather than make the cake taste of coffee.
• Fat: rapeseed oil is preferred to butter here because it keeps the crumb softer and moister, especially with GF flour and reduced sugar.
• Eggs: whisk the whole eggs well with the sugar/sweetener to build some air, but this isn't intended to be a foam sponge.
• Buttermilk: goat buttermilk is ideal; if unavailable, acidulated goat milk works well.
• Do not overmix once the flour goes in — fold gently, as overmixing GF batter can make the crumb heavier.
• Do not overbake — the cake should come out with a few moist crumbs. Overbaking will show more because the sugar is so low.
• Mousse chocolate: use a 50:50 mix of 75% and Green & Black's 85% for a dark flavour without making the mousse unnecessarily firm or bitter.
• Mousse: no added sugar. The whipped egg whites make it lighter and more mousse-like; the chocolate gives enough firmness for layering once chilled.
• Egg whites: use fresh pasteurised egg white if serving anyone for whom raw egg is a concern.
• Mousse consistency: chill briefly before filling — it should be fluffy but hold a mound on a spoon.
• Filling depth: divide between the two layers rather than making very thick mousse bands, to reduce bulging.
• Ganache: use whipping cream, not single cream, for a smoother, more reliable drip without being as rich as double cream.
• Ganache chocolate: again use the 75%/85% blend.
• Ganache consistency: test one drip before covering the whole cake. The cake must be well chilled first.
• Assembly: leave roughly 1cm clear around the edge when spreading mousse, as the weight of the next layer will push it outward slightly.
• Chilling: chill after filling and again after adding the ganache.
• Serving: remove from the fridge around 20–30 minutes before serving for the best sponge and mousse texture.
• Storage: keep refrigerated because of the cream and mousse filling.
• Best eaten: same day or the following day. The oil-based sponge should remain softer from the fridge than a butter-based version.