Wash the potatoes and cook in boiling water for about 20 minutes. Quench, peel and slice.
Peel and finely chop the onions. Finely dice the bacon and fry it crisply in a large pan. Fry the onions briefly. Remove from the pan.
Heat 3 tablespoons of clarified butter in a frying pan. Fry the potatoes in it in portions until crispy. Season with salt and pepper. Mix potatoes and bacon mixture. Put them into a round tart dish (26 cm Ø; 3.5 cm high; alternatively into a casserole dish).
Whisk eggs and cream. Season with salt and pepper. Pour over the potatoes. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for 35-40 minutes.
Stir together the sour cream and mustard. Season with salt and pepper. Dice cucumbers. Wash the meat, dab dry and cut in half crosswise. Mix flour, salt and pepper. Turn meat in it.
Heat 3 tablespoons of lard in a frying pan. Fry half of the escalopes in it on each side for about 2 minutes. Take them out and keep warm. Fry the remaining schnitzels in the same way. Wash and chop the parsley.
Arrange gratin, schnitzel and mustard cream. Sprinkle with parsley and cucumber cubes. Garnish as desired with tomato and cucumber fan.