Preparation time : 12 hours + 8 hours
Cooking time : 40 min + 40 min
Prepare the ganache the day before.
Heat the cream with the grated tonka bean. Once it has come to the boil, remove from the heat, add the chocolate and stir, taking care to incorporate as little air as possible, until the mixture is homogenous.
Cover the surface of the batter with plastic film and refrigerate for 12 hours.
The next day
Preheat the oven to 165°C.
In the bowl of a stand mixer, combine the eggs and sugar. Beat the mixture to the ribbon (until thick and creamy, leaving the trace of a ribbon in the bowl).
Sift the flour over the mixture while gently folding it in with a rubber spatula so that the batter does not collapse.
Adjust the DEBUYER expandable pastry frame to 20 x 20 cm. Line with baking paper and grease.
Transfer the batter to the mould and bake for 40 min.
Unmould the sponge and place on a cooling rack. Let cool at room temperature.
Prepare the chocolate sponge, following the same steps as for the regular sponge, but combining the cocoa with the flour before folding it in.
For the glaze
In a mixing bowl, combine the icing sugar and milk and whisk until the mixture is homogenous.
Slice the plain sponge in half horizontally.
Place one slice of plain sponge in the DEBUYER expandable pastry frame.
Cover with half of the ganache prepared the day before and top with the chocolate sponge.
Spread with the rest of the ganache and top with the second slice of plain sponge.
Top with the glaze and decorate with the chocolate sprinkles.
Refrigerate for 4 hours.
Unmould the Neapolitan cake and serve.