Peel, wash and quarter the potatoes and boil them in salted water for about 20 minutes. Add frozen peas about 5 minutes before the end of the cooking time and cook with them.
Pat the steaks dry. Cut the fat edge several times. Season steaks with salt and pepper. Heat oil in a pan. Fry the steaks for 2-3 minutes on each side. Drain the potatoes and peas and let them drip off.
Add 3 tablespoons of butter and milk. Mash everything coarsely. Season to taste with salt and nutmeg. Take out the steaks.
Heat 1 tablespoon of butter in hot frying fat. Add fried onions. Cut the steaks into strips and toss in the roasted onion butter. Serve everything.