Peel, wash and coarsely chop the potatoes. Cook in salted water for about 20 minutes. Wash and halve the tomatoes. Clean, wash and shake dry the arugula. Pluck a little smaller if necessary.
Heat 1 tablespoon of oil in a frying pan. Fry the sausages for about 6 minutes. Remove and keep warm. Heat 1 tbsp. oil in the frying fat. Fry the tomatoes in it. Add rocket salad and fry briefly. Drain the potatoes.
Add milk and butter. Mash everything. Season to taste with salt and nutmeg. Fold in tomato-rocket mixture. Serve everything.