Clean and wash the Brussels sprouts and cook in salted water for about 20 minutes. Wash the meat, dab dry. Season with pepper. Fry the fillet of beef in 2 tablespoons of hot oil all around. Then fry over medium heat for 25-30 minutes.
Add pork fillet after 10 minutes, chicken fillet after 20 minutes and fry. Season with salt. Peel potatoes, cut in half and fry in a large pan in remaining hot oil for about 15 minutes.
Add Brussels sprouts, mushrooms and onions. Season with salt and pepper. Keep meat warm. Add frying stock to vegetables and continue frying for about 5 minutes. For the sauce heat 1/8 litre of water. Stir in sauce powder.
Bring to the boil and fold in the butter in pieces at low heat. Cut the meat open. Serve with sauce and vegetables.