Knead flour, butter in flakes, egg yolk, 1 tablespoon of water and 1/4 teaspoon of salt to a smooth dough. Wrap in foil and chill for about 30 minutes. In the meantime clean, wash and cut leek into rings. Cook in boiling salted water for 5 minutes and drain. Whisk eggs and sour cream. Season with salt, pepper and nutmeg.
Roll out the dough thinly to 8 circles (approx. 14 cm Ø) on a lightly floured work surface. Place in greased, flour-spread moulds (approx. 12 cm Ø). Press the edges firmly and smooth down the excess dough. Prick the dough several times with a fork. First spread ham and leek, then the icing in it. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 20 minutes