Fold your prepared fruit purée into the whisked egg foam. Pour the mixture into a saucepan and heat, stirring constantly. You need to reach exactly 85°C so the custard thickens without the eggs curdling.

As soon as the custard reaches the right temperature, take it off the heat immediately. Stir the bloomed gelatine into the hot mixture. Mix thoroughly until the gelatine has completely dissolved without a trace.

Let the mixture cool to 40°C. Only then add the cold butter, cut into cubes. Blend everything with a hand blender into a smooth emulsion. This will give the custard a perfectly silky, glossy finish.

Transfer the finished custard to a clean container and cover with plastic film, pressing it directly onto the surface of the custard. Chill in the fridge for at least 2 hours so it sets perfectly and is easy to pipe or fill with.

While the custard is setting, move on to the dough. Blitz the sponge biscuits into a very fine powder. The finer the mixture, the easier the dough will be to work with, and the smoother the surface of your nests will be.

Melt the white chocolate together with the butter over a bain-marie, taking care as you go. White chocolate is sensitive to high heat and scorches easily, so keep a close eye on the temperature.

Add icing sugar and a pinch of salt to the blitzed sponge biscuits to bring out the flavour. Pour in the melted chocolate mixture. Work the dough together with your hands. If it's too stiff, add milk a teaspoon at a time, but go carefully!

Wrap the finished dough in plastic film and chill in the fridge for 10–15 minutes. The chocolate will firm up in the cold, making the dough much easier to handle. Don't leave it too long, though, or it will turn too hard to work with.

Pinch off small pieces of dough, dust the mould with icing sugar, press the dough into it, make a small dip in the centre, fill with the mango custard and top with a sponge biscuit. Store in the fridge.