Gently whisk together the flour, sugar, baking powder and salt. Create a well in the middle, add the egg, yolk and butter cut into pieces.
Grease and flour 8 medium tart pans or 12 medium muffin tins.
Cut out circles with a large round cutter and place them into the prepared pans. Refrigerate until the cream filling is ready.
Fill the cups with the filling and bake.