Peel onions and cut them into fine rings. Clean the mushrooms, wash if necessary, cut in half.
Peel and finely chop the onion. Knead with mixed mince, 1 egg, breadcrumbs and mustard. Season with salt and pepper. Form 4 large meatballs from the minced meat mixture.
Fry the meatballs in 2 tablespoons of hot oil for about 10 minutes. Take out, keep warm.
Heat 1 tablespoon of oil in hot frying fat. Sauté onions and mushrooms in it while turning them. Season with salt and pepper. Deglaze with sherry. Add 200 ml water and cream, bring to the boil and simmer for about 3 minutes. Mix starch and 2 tbsp. cold water. Stir into the boiling mushroom sauce and continue to simmer for about 1 minute while stirring. Season to taste with salt and 1-2 tsp. coarse pepper.
Wash oregano, shake dry and pluck leaves from the stalks. Arrange the meatballs with mushroom-pepper cream, sprinkle with oregano. Mashed potatoes and cranberries taste good with it.