Soak the sweetbreads in cold water to remove any impurities and then place them in cold salted water. Bring to a bare simmer for 5 minutes; refresh in ice water and weight them down. Split the sweetbread rounds in half and stuff them with the slices of the andouille; season.
Heat a drop of oil with 20 g butter in a non-stick pan; sauté the sweetbreads while basting them continuously with the remaining butter.
Making the chutney: Sweat the onions in the butter; add the sugar and vinegar, and at the end, the finely chopped apples. Cook 10 minutes.
Presentation: Place the chutney in the middle of the plate, arrange the sweetbreads on top, and spoon around them the reduced veal juices combined with some uncooked cider.