Tápai potato pastry

Dough:

Make a leavened dough from 400g flour, 3dl milk, a pinch of salt and 15g developed yeast. Add 100g fat or 120g melted butter. Raise the dough, roll it out and put it in a 25cm ´ 40cm baking pan.

Filling:

Boil 5 (approx. 400g) medium large (old) potatoes and mash them Add 100g butter, 3dl good-quality sour cream, 2 eggs, 1 table-spoon of flour, + 1 egg and season the filling with a pinch of salt. Stir it smooth.
Put the filling on the leavened dough and bake it in the oven of medium temperature.
It can be made sweet if you put some sugar in the filling to taste.
The baked cake can also be sugared.