Trim, wash and slice the leeks. Preheat a large pan or skillet, then add cooking oil. Add the onion and leeks and cook until they are wilted, about 5 minutes or so. Season lightly. Add the wine and stock and simmer for about 10 minutes
Peel and dice the potatoes, add them and simmer for about 10 minutes more or until barely cooked
Prick the sausage with a fork and sit it on top of the vegetables. Cover and simmer for about 20 minutes
Lift out the sausage. Stir the cream into the vegetables. Slice the sausage and put them back into the pot and serve