Peel the potatoes, place them on a spoon and cut them close together until the edge of the spoon. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for about 30 minutes. In the meantime, stir the quark, mineral water and lemon juice until smooth.
Wash herbs, chop, stir in. Season with salt and pepper. Wash the steaks and dab dry. Heat oil in a coated pan and fry the steaks on both sides. Season with salt and pepper.
Fry over medium heat until done. Wash lettuce leaves and dab dry. Peel and chop the onion. Whip with vinegar and remaining oil. Season with salt and pepper. Marinate salad with it. Arrange everything on plates and serve garnished with lemon wedges.