More than 1 hour (plus chilling time)
- 300g chocolate cookies, crushed (we used Oreos, with the icing removed)
- ½ cup (125g) butter, melted
- 3⅖ cups (800ml) cream, chilled
- ¼ cup (60ml) castor sugar
- Seeds of 1 vanilla pod (or 2 tsp (10ml) vanilla extract)
- 300g milk chocolate, chopped
- 300g dark (70-80%) chocolate, chopped
- 14g gelatine powder (combined with 3 Tbsp water to sponge)
- ¼ cup (60ml) strong coffee, cooled to lukewarm
- ⅓ cup (80ml) cream
- 200g white chocolate, chopped
- Blitz cookies until fine, add melted butter and stir to combine.
- Press into a 20-23cm loose-bottomed cake tin lined with baking paper.
- Whisk cream, castor sugar and vanilla to medium stiff-peak stage.
- Divide mixture between two bowls and chill in fridge.
- Melt dark chocolate in a glass bowl over a pot of boiling water until smooth. (This is the best way to melt chocolate as the heat is more even than in a microwave.) Set aside.
- Add sponged gelatine to lukewarm coffee.
- Microwave for 20-30 seconds, or heat in a pot over low heat, just until gelatine melts – don’t let it get too hot.
- Halve gelatine-coffee mixture.
- Whisk half the mixture vigorously into melted dark chocolate, then whisk into bowl of chilled cream until smooth.
- Spoon over cookie base in cake tin and chill for 20 minutes.
- Repeat process with remaining gelatine, milk chocolate (melted) and chilled cream, spooning mixture on top of semi-set dark chocolate layer.
- Chill mousse cake for 3-4 hours, or overnight for best result.
- For ganache, heat cream to hot but not quite boiling.
- Pour over white chocolate in a bowl and stir until melted.
- Set aside to cool to room temperature.
- Pour cooled ganache onto cake, spreading over the entire surface. (Work quickly, as the cold cake can make ganache set quicker.)
- Chill cake for another 30 minutes.
- Run a warm cloth around outside of cake tin, then run a hot knife inside around the rim to loosen cake.
- Remove from tin and slice with a slightly warmed knife (wipe the blade clean between every cut for perfect slices)