Peel the potatoes, cook them in plenty of salted water, mash them, add the butter and milk and stir to make a puree. Salt and pepper.
Fry the sausages and keep warm.
Pour off the fat except for 2 tablespoon. Fry the onions until golden, add the meat stock and simmer for 5 minutes. Add the sausages and bring to the boil briefly.
Serve on top of the mashed potatoes. Sprinkle with parsley.