Make a batter out of the quark, milk, olive oil, 1/2 teaspoon sea salt, wholemeal flour, baking powder and an egg and place in a greased springform pan. The edge should be pulled up 3 cm.
Stew the leek, onion, water and mustard seeds in a saucepan until the leek is firm to the bite. Place the vegetables on the batter in the springform pan.
Mix the 3 eggs, sour cream, yoghurt and the spices in a bowl and mix in the cheese. Put this mixture in the springform pan on top of the leek.
Bake the whole thing in a preheated oven at 150 ° C for about 1 hour.