Mix the crumbled shortbread biscuits with the melted butter in a medium-sized bowl and press onto the bottom of a greased springform pan. It is an advantage to use one of the American aluminum pie tins, but it also works with a springform pan, you just have to press the mass up a little to the edge.
Now mix the cream cheese and sugar in a large bowl until smooth, add milk. Now only add one egg at a time and mix. Now add the sour cream, flour and vanilla sugar and stir everything again.
Now pour the mixture onto the dough base and put it in the oven.