Melt the fat, add the sauerkraut and tomato paste. Steam for 10 minutes, season with salt and pepper. Cut the rolls open, place the lower halves on a baking tray covered with baking paper.
Cut the sausages in half. Put some sauerkraut and 1/2 sausages on the lower halves of the rolls, sprinkle the cheese on top. Bake in the preheated oven (electric: 200 °C / gas: level 3) for 10-15 minutes.
Place the top halves of the rolls on the baking tray and bake for 10 minutes. Wash the tomatoes and chives. Slice the tomatoes and cut the chives into small rolls. Mix mayonnaise and mustard, place on the lower halves of the rolls, sprinkle with chives and cover with the upper halves.
Serve the rolls with tomato slices, remaining chives and parsley.