Peel, wash and chop the potatoes. Cook potatoes in salted water for about 20 minutes until soft. Clean, wash and drain the salad well. Heat milk and butter in a small pot.
Roughly mash the potatoes and mix with the milk. Fold in 100 g salad and season to taste with salt, pepper and nutmeg. Keep warm.
Onions peel, halve and in fine slices cut. Heat 2 tablespoons of oil in a small pot. Fry the onions in it. Sprinkle with sugar and caramelize. Deglaze with port wine and vinegar and simmer for about 30 minutes.
Heat 2 tablespoons of oil in a frying pan. Fry the sausages until crispy brown, turning them over.
Finely slice the parmesan. Carefully mix the remaining lamb's lettuce and onions, season with salt and pepper. Arrange mashed potatoes, sausages and salad on plates. Sprinkle salad with parmesan.