Clean and wash the Brussels sprouts, cover and cook in a little salted water for about 15 minutes. Peel, wash and roughly dice the potatoes, cover and cook in boiling salted water for about 20 minutes.
In the meantime peel and finely dice the onion. Rinse meat, dab dry and cut into strips. Heat the oil in a pan. Fry the meat in it at high heat for 3-4 minutes. Season with salt and pepper. Take out.
Drain the Brussels sprouts. Fry the onion and Brussels sprouts for approx. 3 minutes in the frying oil while turning. Sprinkle with sugar and continue frying for 2-3 minutes. Add vinegar, 1⁄8 l water and meat and simmer for 5 minutes open. Season everything with salt and pepper.
Drain the potatoes. Add milk and mash everything. Season to taste with salt and nutmeg. Serve everything.