Put the flour like a fountain on the work surface, make a hole in the center and add an egg, sugar, vanilla, lemon zest and diced butter.
Work the ingredients quickly with your hands and form a smooth ball; put it in the fridge for 30 minutes, wrapped in transparent film.
Put the ricotta in a bowl and mix with the egg, sugar, liqueur and flour. Grate 50 g of chocolate and add it to the mixture.
Grease a round opening mold (20 cm in diameter) and sprinkle the ricotta mixture on the bottom, leveling it well with a spoon.
Take the dough out of the refrigerator and make small balls the size of a walnut.
Distribute them over the ricotta mixture and bake at 180 ° C for 30 minutes.
Allow the cake to cool, then carefully remove it from the mold.
Sprinkle with chocolate powder. Melt the remaining chocolate in a bain-marie with a knob of butter and let it fall flush with a spoon over the cake.