Wash the leek, cut into fine rings and sauté in the oil for 3-4 minutes, then season with salt and pepper. Now mix the sour cream with the mustard.
Place a slice of meat loaf on each slice of bread, spread the leek and sour cream mustard cream on top, place the bread on a baking sheet lined with baking paper and place in the preheated oven at 150 ° C for about 15 minutes.