Before lighting the grill, line the warming rack of your grill with a sheet or two of tinfoil. Preheat your grill to 400°F, using only two burners.
Using a sharp knife, carefully cut an ‘x’ into the top or side of each fresh chestnut.
Place all of the chestnuts on the warming rack of the grill and roast them until the cuts have split open and the interior nut is tender, 40 minutes or so. Once done, remove the nuts to cool until you can handle them safely.
While the chestnuts are roasting, slice the bread into bite sized chunks, season with garlic butter, sage, and then salt and pepper to taste. Place onto a baking sheet and using indirect grilling, bake the bread until crispy.
Turn the grill down, and allow it to cool to 350°F.
While the chestnuts are roasting over your grill’s open fire, grill the sausages over direct heat until sear marks form and they get a little smoky.
Crack the shells off of the nuts, and chop them into bite-sized pieces.
Remove the casings and finish the sausages in a frying pan. Add the onion and celery and continue to cook over medium heat until the celery and onion are tender. Deglaze the pan with the white wine, allowing it to reduce by half.
Toss the sausage and veggies, toasted bread, and chopped chestnuts together in a large bowl. Pour over the chicken stock and mix well. Pour the stuffing mixture into a greased baking dish, cover with foil and bake over indirect heat for about 30 minutes. Uncover and bake until the top is crispy.
Serve this as a great side for any family meal, topped with fresh parsley as a garnish.