I’m always in absolute awe of Heston Blumenthal’s recipes and approach to cooking – he is a genius in modern cooking and makes everything so thought-worthy. Added to that, I love his reductionist methods that get into the basics behind the recipes he creates. As an ex-lab-rat scientist, this really appeals to me. I’ve seen this cake made on one of Heston’s TV shows, involving a spray paint can and requiring a lot of outdoor space… so like most of Heston’s recipes, I thought, not for me…. But from Heston’s original (I think) recipe, this sublime, rich chocolate mousse cake with a silky hit of chocolate glaze on the top and a bit of a surprise in the base, is surprisingly easy to make!
I was a bit nervous about making the chocolate mousse using dark chocolate with 55% cocoa solids, thinking it would be too strong for a dessert for kids, so I made a 50:50 mix of dark and white chocolate, using regular (35% fat) cream and created a marbled pattern. The cake is best eaten the day you make it, to maximise the effect from the popping candy. Using coated popping candy really helps to keep it ‘fresh’ and I wouldn’t recommend using untreated popping candy (such as ‘pop rocks’), as they will lose their pop pretty quickly. That said, if you buy ‘pop rocks’ or similar, it is not too hard to make your own coated popping candy using chocolate (instructions below).
Heston’s popping two-chocolate mousse cake
- 100 g Marie biscuits
- 30 g butter, melted
- 50 g milk chocolate, melted
- ½ teaspoon ground ginger
- 1 teaspoon mixed spice
- 50 g hazelnut meal
- 25 g coated popping candy
- 100 g dark chocolate (55% cocoa solids)
- 100 g couverture white chocolate (> 32% cocoa butter)
- 300 ml 35% fat cream
- 85 g golden syrup
- 120 ml water
- 4 coffee beans (or use 1 teaspoon freshly ground coffee tied up in cheesecloth)
- 20 g Dutch cocoa
- 20 g dark chocolate (55% cocoa solids), finely chopped
- pinch salt
- Line the bottom and sides of a small (18 cm diameter) loose bottom cake tin with baking paper, ensuring some baking paper extends over the top.
- Place the biscuits, butter, milk chocolate, ginger, mixed spice and hazelnut meal in a food processor and blitz until all combined and you have a course texture.
- Fold through the popping candy and spoon into the base of cake tin, pressing down gently to make a flat crust.
- Place in fridge to set.
- To make the two-chocolate mousse, break up (or grate) the dark chocolate into small pieces in one heat-proof bowl and break up (or grate) the white chocolate into small pieces in a separate heat-proof bowl.
- Heat 100 ml of cream in a pot on the stove top until steaming (but do not let it boil).
- Pour half the hot cream on the milk chocolate and the remainder onto the white chocolate.
- Mix each until smooth, then add a small pinch of salt to each.
- Allow to cool to room temperature (but do not let the chocolate set!).
- Meanwhile, whip the remaining 200 ml cream until soft peak form. Split into two halves.
- Gently fold each chocolate into each half of the cream.
- Spoon the white chocolate mousse over the crumb base, then add the dark chocolate mouse and stir a few times in a swirling pattern to create a ripple effect.
- Return mousse cake to fridge to set for an hour.
- To make the glaze topping, heat the golden syrup in a pot on the stove until boiling, then remove from heat and carefully add the water, coffee and cocoa, mixing until the cocoa is fully dissolved.
- Pour over the dark chocolate in a heat-proof bowl and stir until the chocolate is melted. Add a pinch of salt to taste.
- Pass through a fine sieve and when it has cooled to tepid, pour over the mousse to create a glaze. Return to fridge (the glaze will remain slightly sticky).
- When ready to serve, unmold from the cake tin and carefully remove the baking paper.
Hint: making your own coated popping candy using packet ‘pop rocks’ or similar is quite simple. Melt 50 g white chocolate to 40°C, allow to cool to 25°C, then warm again to 28°C (this tempers the chocolate). Spread half thinly on a sheet of baking paper and smooth out with a palette knife. Sprinkle a couple of packets of popping candy evenly over the top of the melted chocolate, then spread over the rest of the melted white chocolate, ensuring the popping candy is coated. Leave to set at room temperature. Break or crush up the chocolate to use as required!