In a large frying pan, melt butter, and caramelize onions.
Brown sausage in batches, and remove as they brown.
Deglaze pan with the apple juice, and add the onion soup.
Stir soup until dissolved, and add apples.
Return sausage to pan and cook, covered, until sausage is cooked completely through and apples are just soft, about 20 minutes
Remove sausage to serving dish.
Add corn starch dissolved in water into the sauce, stirring rapidly as you pour it in. Thicken the sauce; another 5 to 10 minutes of cooking.
Pour sauce, apples and onions over the sausages; serve and enjoy!