First make the dough. For this, knead cold butter with flour, egg, salt and crème fraiche and put in a cool place for 1-2 hours.
For the topping, cut the leek into fine strips and sauté lightly with the finely diced onions and bacon cubes in heated oil.
Beat the eggs well with crème fraîche , salt and pepper. Roll out the dough to a thickness of about 5 mm and line the buttered quiche dishes with it.
Divide the bacon and leek filling among the dishes and then fill with the glaze. Bake in the preheated oven at 200 °C top/bottom heat for approx. 30 minutes.