Put flour, 250 g fat and 1 teaspoon salt in a bowl and knead with your hands. Add 2 eggs and 3 tablespoons of cold water and knead to a smooth dough. Cover and put in a cool place for at least 1 hour. Meanwhile clean and wash the leek, drain well and cut into rings. Peel onions and cut them into rings as well. Heat the remaining fat.
Steam leek and onions for 5-8 minutes. Season with salt, pepper and thyme and let cool down. Wash parsley, dab dry and chop, except for a little bit for garnishing. Roll out the shortcrust pastry on a greased fat pan and press the pastry slightly up at the edges. Prick the base several times with a fork. Pre-bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 20 minutes. In the meantime, mix the sour cream and remaining eggs. Season with salt, pepper and nutmeg. Cut the camembert into slices, possibly halve it. Grate Gruyére. Stir the Gruyére and parsley into the leek and onion mixture and add to the dough. Spread the camembert on top and pour the sour cream mixture over it.
In the meantime, mix the sour cream and remaining eggs. Season with salt, pepper and nutmeg. Cut the camembert into slices, possibly halve it. Grate Gruyére. Stir the Gruyére and parsley into the leek and onion mixture and add to the dough. Spread the camembert on top and pour the sour cream mixture over it. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for another 25 minutes. Cut hot cheesecake into approx. 18 pieces and serve garnished with parsley