For the crust:
Beat the egg, sugar, and salt in a bowl until the mixture is foamy.
Add the flour all at once and mix with a spatula, then knead the dough with your hands.
Add the butter and knead to obtain a homogeneous dough and shape into a ball.
Wrap the dough in plastic wrap and refrigerate for 1 hour.

Pastry cream (to be prepared in advance so it’s cold):
Heat the milk and vanilla until boiling point.
Meanwhile, combine the egg yolks, sugar, and flour and mix well until you get a smooth mixture

Pour the hot milk slowly into the egg mixture and mix well.
Transfer the mixture to the saucepan and let it thicken over the heat without stopping to mix with a whisk.
Cover the saucepan with plastic wrap and let it cool completely.

Roll out the dough with a rolling pin, on a floured surface, and then fill a 9″ (23cm) diameter tart mold.
Poke the bottom of the tart with a fork and bake for 20 minutes in a preheated oven at 350°F (180°C).
Remove the crust from the oven and fill it with pastry cream up to 1/2″ (1cm) from the edge.
Sprinkle the top of the pastry cream with crushed Daims, then put it back in the oven at 350°F (180°C) for 8 minutes.

Melt the chocolate and butter in a double boiler, then pour the mixture over the tart and smooth with a spatula.
Let it cool completely before cutting into slices.