Crumble flour, cubed butter, salt and sugar in a bowl.
Add egg and knead to a dough.
Cover up and place in fridge.
Dilute custard powder and sugar in some milk.
Bring rest of milk and egg liqueur to boil.
Pour diluted custard in hot milk while stirring.
When thickend, put aside.
Crumble flour, cubed butter, sugar and salt in a bowl.
Roll out shortcrust on a floured surface and put in a tart or spring form. 26cm Ø
Use rest of shortcrust for cookies. (Cut out shapes and bake.)
Stir custard and spread on shortcrust.
Spread crumble on top.
Bake in preheated oven at 180°C for about 45 minutes.
Sprinkle powdered sugar on top.