Peel and wash the potatoes, cut into large pieces and cook in boiling salted water for about 20 minutes. Drain, allow to evaporate well and press through a potato press.
Let the potato mixture cool down for about 5 minutes. Melt butter in a small pot and remove from the heat. Wash parsley, shake dry and chop finely, except for a few leaves for garnishing.
Add egg yolks, liquid butter, semolina, flour and chopped parsley to the potato mixture, mix thoroughly with your hands, season with salt.
Cut the blood sausage into small pieces. From the potato mixture, with moistened hands, divide into 12 equally sized pieces, press them slightly flat, fill them with black pudding and form them into dumplings again. Bring salted water to the boil in a large pot, cook dumplings in boiling water in 2 portions for about 10 minutes.
In the meantime, peel the onions and cut them into slices. Peel and finely chop the garlic. Heat oil in a pan. Fry the onions and garlic in it until transparent, turning them over. Deglaze with broth.
Stir in processed cheese, heat up. Add spinach and stir occasionally. Cook for about 8 minutes. Season to taste with salt and pepper.
Lift the dumplings out of the pot with a skimmer, drain and arrange on plates with the creamed spinach. Garnish with parsley leaves.