Season the pork medallions and fry in oil on both sides. Take out and wrap in aluminum foil.
Melt the butter in the frying stock and sauté the onion. Deglaze with a dash of white wine and let it boil down briefly. Pour the soup on top and let it boil down for approx. 5 minutes. Then stir in the remaining ingredients and season to taste.
Put the meat in the sauce and heat or steam to the desired degree (pink or well-done).