4 persons

1. Wash the leeks, remove any root and the ends of the leaves, cut into pieces 1-2 inches long
2. Sauté the onion in half the butter for five minutes, without letting it color. Add leek and allow to stew together for 2-3 minutes, stirring continuously
3. Season with salt and pepper, add wine and bouillon, and cook covered for another 15 minutes
4. Add the potato, cook for another 10 minutes
5. Add the sausages and simmer in the leek mixture for 20 minutes
6. Heat the remaining butter in a second pan. Add flour, cook together for 2-3 minutes, stirring constantly, then add milk and 10 fluid oz of the liquid from the leeks
7. Mix together well, season with salt, pepper and nutmeg, and cook gently on a low heat for 10 minutes
8. Put the leek mixture and sausages in a sieve and drain well, retaining the cooking liquid (which can be used to make soup).
9. Stir the leek mixture into  the milk sauce, and simmer for another 5 minutes with the sausages. If the sauce is too thick, dilute with some of the liquid used for cooking the leeks.  
10. Remove the sausages, rinse them briefly in hot water.
11. Arrange the leeks on a serving dish, lay the sausages on top.
12. Pierce the sausages once or twice with a fork, so that the juice does not spurt out when they are cut, but pours over the vegetables.
13. At table cut the sausages on a board.