Knead flour, fat, 1 egg and salt with the dough hooks of the hand mixer to a smooth dough. Wrap in foil and chill for about 45 minutes. Meanwhile cook potatoes in boiling water for about 20 minutes.
Clean, wash and cut the leek into pieces. Peel onion and garlic and chop finely. Knead minced meat and tomato paste. Season with salt and pepper. Heat oil in a pan and fry onion and garlic.
Add the mince and fry until crumbly. Take out and let cool a little. Sauté the leek in the frying fat for about 4 minutes while turning. Remove and drain well on kitchen paper. Drain potatoes, rinse with cold water and peel.
Cut the potatoes into slices. Knead dough on a floured work surface until smooth and roll out round (approx. 30 cm Ø). Place the dough in a greased, round quiche tin (26 cm Ø), pressing the rim down.
Put the potatoes, minced meat and leek on the floor. Whisk 4 eggs and milk. Season with salt, pepper and nutmeg. Pour egg milk into the mould. Cook the quiche in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) on the lower level for about 1 1/4 hours.
Remove and serve garnished with parsley.