For the sweet cacao crust:
Add each ingredient, one by one, in the order indicated. Mix well.
When the dough is smooth, let it rest for 3 hours in the fridge.
Roll the dough very thin (around 2mm) and make 5cm rounds with the aid of a fluted cookie cutter.
Bake in a 170°C oven for 7 minutes.
For the creamy chocolate filling:
Make a custard by first beating the egg yolks with 20g of the sugar. Then heat the milk, cream and the rest of the sugar. Once the liquid comes to a boil, slowly pour half of it over the yolks and blend well. Pour this mixture back into the pan, then heat on low (84°C) until the custard coats the back of a spoon.
Pour the custard over the chocolate.
Mix with an immersion blender.
Let the custard rest 8 hours in the fridge.
For the chocolate discs:
Melt the chocolate.
Pour the chocolate onto a sheet of plastic dipping paper or silicone mat.
Spread thinly.
When the chocolate begins to harden, cut out circles with the same fluted cookie cutter used for the cacao biscuit.
Assembly:
Using a pastry bag, pipe the creamy chocolate filling onto the cacao crust (as if making macarons).
Then place a chocolate disc on top of each one.