Preheat the oven to 375°F.

Coat a large wide pot with olive oil and toss in the onions and celery. Season with salt and cook veggies over medium-high heat until soft and very aromatic, 8-10 minutes. Add the garlic and cook for an additional 1-2 minutes. Add the mushrooms and cook for 3-4 minutes.

Add the sausage and cook until it's really brown and yummy, 12-15 minutes. While the sausage is cooking, break it apart with a metal spoon or spatula — you want the meat in pretty small pieces.

Add the white wine and cook until it has evaporated by half. The mix will be pretty soupy — that's okay.

In a large bowl, combine the bread with the sausage mixture. Toss in the sage and walnuts and pour about half the chicken stock into the bowl. Using your hands, work to combine everything well — really get in there and squish it up, it's fun! Add the remaining stock as needed to create a really moist mix. Taste and season with salt, if needed . . . it will be.

Transfer the mixture to a large baking dish and cover with foil. Bake for 30 minutes or until the stuffing is hot all the way through. Remove the foil and bake for another 15 minutes to brown the top.