Pour the flour into a bowl, dice the butter and knead with the salt and egg to form a smooth dough. Cover and let rest in the refrigerator for 30 minutes.
Clean the leek, mushrooms and zucchini and cut into small pieces. Fry the zucchini and leek first, then add the mushrooms and fry until cooked through. Peel and squeeze the garlic. Season with salt and pepper to taste.
Preheat the oven to 200 degrees. Grease a mold, distribute the quiche dough evenly in it and form an edge. Put the fried vegetables in the pan and distribute them.
Whisk the sour cream with the eggs, season well with salt, pepper and nutmeg and pour over the vegetables. Bake in the middle of the oven at 180 degrees for 40 minutes until golden brown.