Wash the potatoes and cook covered for 20 minutes. Quench, peel, halve and let cool down a little
Dab the steak dry and cut into strips. Clean and wash the mushrooms and peppers. Halve the mushrooms and dice the bell peppers finely. Peel and slice the onion. Cut cucumbers into slices
Heat the oil in a coated pan. Sauté the meat briefly and thoroughly. Season with salt and pepper, remove
Fry the mushrooms, onion, potatoes, bell pepper and cucumber in the frying fat. Season everything with salt and pepper. Stir in about 1/8 l water and mustard. Bring to the boil, cover and stew for about 5 minutes. Add meat again and heat up. Season to taste