Chocolate and rum black bottom pie

Melt the butter gently in a small saucepan. Heat a conventional oven to 175 °C. Crush the biscuits and mix with 25 g sugar and the melted butter. Press over the base and sides of a deep 23 cm tin, about 5 cm high for the family-size guide. Bake for 10 min, then cool on a rack for about 30 min.

Sprinkle the gelatin over the cold water mixed with rum and let hydrate while making the custard. Mix 133 g sugar with the cornstarch, then whisk in the milk. Separate and weigh the yolks, add them and heat over medium heat, whisking continuously. When boiling begins, cook for 1 min. Off the heat, stir in the hydrated gelatin until completely dissolved.

Chop the chocolate. Weigh the cooked custard and divide into 3 equal masses. Mix 1 still-hot portion with the chopped chocolate until fully melted. Spread in the cold biscuit crust and refrigerate for about 30 min until this layer sets. Let the remaining custard reach room temperature without setting completely.

Whip the cold cream with the icing sugar to soft peaks. Weigh the finished whipped cream and divide into 4 equal masses. Gently fold 1 portion into the cooled rum custard and spread over the set chocolate. Keep the remaining whipped cream covered in the fridge.

Refrigerate for at least 2 hours until the mousse sets. Spread the remaining whipped cream on top just before serving and slice cold. Refrigerate covered leftovers.