- Preheat oven to 165C.
- For the mousse, melt chocolate in microwave in bursts on low heat, stirring regularly. Set aside to cool slightly. Place egg yolks and 30 grams sugar in a bowl over a pan of simmering water and whisk until light. Remove from heat and cool slightly. Whisk egg whites with 30 grams sugar to soft peaks. Fold chocolate into egg yolk mixture then egg whites then cream in 3 batches until combined. Transfer to a lined 21cm x 31cm shallow tray and place in freezer until set. Once set, break into rough chunks then toss in cocoa powder. Shake off excess cocoa then set aside in the freezer.
- For the crumb, combine all ingredients in a small food processor and blitz until crumbly. Transfer to a paper lined baking tray and bake until golden, about 20 minutes.
- For the crème patissiere, bring milk and vanilla to a simmer in a small saucepan. Meanwhile whisk egg yolk with sugar, add cornflour and mix to a paste. Add hot milk to egg yolk mixture, whisking continuously. Return mixture to pan and cook over medium heat, whisking continuously until thick. Add butter and mix through. Set aside.
- For the vanilla cremeux, fold whipped cream into crème patissiere mixture. Place in fridge to chill.
- For the hazelnut cremeux, whisk nutella through crème patissiere then fold in cream. Set aside in fridge.
- For the coffee cremeux, combine coffee, sugar and 25ml water in a small saucepan and bring to a simmer. Remove from heat and cool. Add coffee syrup to crème patissiere, fold in cream and chill in fridge.
- To serve, place a dollop of each crème patissiere on each serving plate. Cover with hazelnut soil. Sprinkle with lime zest and mint leaves and place chocolate mousse rocks on top.