1. Cut your loaf of bread into 1/2-inch squares. Bake the squares at 325-degrees until the outsides of the cubes are crisp, around 15 minutes.
2. Increase the oven temperature to 350-degrees.
3. Dice the onion, and the celery. Heat the butter in a medium saucepan, and sauté the veggies. When the onions are translucent and the celery is slightly softened, add the chestnuts and the sausage. If the meat is uncased, just stir it around to make it into crumbles. If it’s in a casing, you can either cut it into rounds and use those, or just squish the meat out of the casing into the pan.
4. Cook, stirring, until the sausage has browned. Add the minced sage.
5. In a large bowl, toss the toasted bread cubes with the onion and sausage mixture. Taste and season with salt and pepper. Pack the stuffing into 9x13 glass pans, cake pans, or whatever else you’d like. Make sure there’s enough room in the vessel for you to stir the mixture every once in a while.
6. Pour in two cups of chicken stock, and stir to moisten all the cubes. Cover with foil, place in the oven, and bake for 30 minutes.
7. Uncover, stir, and taste. If the bread is a pudding-like consistency, return to the oven, uncovered, to let it firm up and brown. If the mixture is a little dry, add more chicken stock, stir, and return to the oven, uncovered.
8. Bake, checking every 10 minutes — and adding stock as needed — until you’ve achieved the classic, evenly moist stuffing consistency. Taste for seasoning once again, and serve.