Wash the leek and cut into rings. Sauté in a little oil. Season and set aside. Roll out the dough or, if already rolled out, place it directly in the round tray (diameter approx. 28 cm) and prick. Whisk the egg with the quark and cream (or milk). Spread the leek on the dough, sprinkle with the grated cheese and pour the topping on top. Briefly toast the pine nuts, spread them on the quiche. Bake for about 30 to 40 minutes at 220 ° C.