Wash the potatoes and cook in boiling water for about 20 minutes. Peel and finely dice onions. Heat the fat in a pan and fry half of the onions in it until transparent. Wash parsley, dab dry and chop except for something to garnish.
Rinse the potatoes under cold water, peel the skin off and mash the potatoes finely. Let them cool down and knead them with the minced meat, egg, breadcrumbs, 50 g cream, steamed onions, half of the parsley and salt to a smooth dough.
Form small balls (approx. 3 cm Ø) with moistened hands and place them on a plate. Cover and put in a cool place for 1 hour. In the meantime clean, wash and drain the mushrooms. Halve the mushrooms.
Heat the oil in a frying pan and fry half of the balls, shaking the pan or turning them carefully until golden brown all around. Keep the finished balls warm and fry the remaining balls in the same way.
For the sauce, braise the mushrooms and remaining onions in hot frying fat and season with salt and pepper. Deglaze with stock and remaining cream, bring to the boil and sprinkle in the sauce thickener while stirring.
Bring to the boil again briefly. Season to taste with salt and pepper. Arrange the meatballs on a plate and pour the sauce over them. Sprinkle with some cranberries and parsley and garnish.
Remaining cranberries extra is enough. Green salad tastes good with it.