If you are making your own bread crumbs, preheat oven to 300F. Cut or tear any type of bread (brioche or french stick is our favourite) into 1/2 inch cubes. Place them in a single layer on a baking tray lined with parchment paper. Cook for 10 minutes - be sure NOT to brown or toast it.
Preheat oven to 350F
Place bacon in a single layer on a baking tray with parchment paper. Cook for 10 min per side. Chop bacon and set aside.
In a large skillet at high heat, allow to get hot. DO NOT ADD any fat and add mushrooms to dry/hot skillet. They will “squeak” which is perfectly normal. Stir mushrooms until cooked - approximately 5-7 min. Allow to cool slightly.
In the same large skillet - reduce to medium heat and add favourite fat (butter, tallow, oil). Add onion, celery, poultry seasoning; cook until tender (or onion becomes slightly translucent) - approximately 10-12 min. Allow to cool slightly.
In a large bowl, combine bread crumbs, onion mixture, mushroom and bacon. Pour 1 cup of water (or broth) overtop and mix together. Add more water (broth) a little at a time until mixture is moist - but not soggy. Add salt and pepper to taste.
Place mixture in a baking dish & cover with foil. Bake for 35 minutes. Uncover and bake for an additional 10 minutes or until brown on top.