For the pastry base: Cream butter with sugar until fluffy.
Add the egg.
Mix flour and baking powder and stir in.
Let the dough rest in the refrigerator for 1 hour. Grease and flour a springform pan (26 cm) with butter, line it with the dough, so also raise the edge. For the filling, mix the curd, eggs, sugar, vanilla sugar and custard powder.
Slowly add the oil and milk while stirring.
This mixture is now very liquid, but that is already right. Pour into the mold and bake at 180° C for about 1 hour on the lowest rack of the oven. It is then still relatively liquid and must therefore remain in the open oven for about 2 hours. The cheesecake is best when it has had time to set overnight.