For the crust: Mix the flour, butter, egg, salt, and sugar into a smooth dough. Wrap in plastic and chill for 1 hour.
Grease the tart pans. Roll out the crust and line the tart pans.
For the filling: Melt the chocolate with the butter in a bowl over a pot of simmering water. Stir in the sugar, salt, and vanilla. Stir in the egg and then fold in the flour and crushed pecans.
Spread the filling into the tart pans. Decorate with the pecans halves and bake in a preheated oven at 180°C (approximately 400°F) for about 20-25 minutes. Remove from the oven and allow to cool in the pans. Serve dusted with cocoa powder.