Dice the beef. Dice 2 onions, cut 1 onion into thin slices. Fry the meat in butter, season with salt and pepper. Add the diced onion, tomato paste and mushrooms, dust with flour and add the beef stock. Season with marjoram and garlic, add black beer. Steam until soft in a pressure cooker for 20 minutes. Roast the onion rings and serve with the sliced cucumber on top when serving.