Grease a tart mould (26 cm Ø) and dust with flour. For the short pastry, put 150 g flour, 75 g sugar, 1 pinch of salt, egg yolk and 75 g butter in pieces in a bowl. Knead first with the dough hooks of the mixer, then with your hands quickly to a smooth dough.
Roll out round (approx. 28 cm Ø) on a well floured work surface. Line the mould with the dough, press down slightly at the edges. Prick the base several times with a fork. Chill for about 45 minutes.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Divide chocolate into pieces for the filling. Melt in a hot water bath and let it cool down a little. Mix cream cheese, 100 g sugar and crème fraiche with the whisks of the mixer.
First stir in eggs, then custard powder. Stir in liquid chocolate in a thin stream.
Pour the cream cheese mixture into the tart mould. Bake in the hot oven on the lower shelf for about 1 hour. Take out, let cool down. Dust with cocoa.