Wash the potatoes and boil in water for about 20 minutes. In the meantime clean and wash the leek and cut it into diagonal rings. Blanch in boiling salted water for about 2 minutes, drain. Wash, clean, quarter and seed the tomato. Cut the flesh into small cubes. Wash and chop the dill. Whisk egg, milk and stock.
Season with salt, pepper and nutmeg. Peel potatoes and cut in half lengthwise. Fill potatoes and leek into a suitable casserole dish. Sprinkle with tomato and dill. Spread egg milk on top. Sprinkle with parmesan. Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 12 minutes