Cut upland bird meat and pork fat into chunks and add to large mixing bowl. Add 1 tablespoon freshly minced sage, 2 teaspoons kosher salt, 2 teaspoons brown sugar, ½ teaspoon paprika, ¼ teaspoon allspice, and 1 teaspoon ground black pepper.
Place mixing bowl with spiced meat in freezer half an hour prior to grinding
Put meat through fine grinding plate and mix with spatula or other kitchen utensil (ideally not hands) after grinding. Place in fridge until ready to cook.
To make gravy, in a large, deep cast-iron skillet heated on medium-low, add 1 tablespoon salted butter followed by one finely minced yellow onion. Lightly salt and pepper. Brown onions and, once fairly soft, add 1½ teaspoons freshly minced garlic.
Stir garlic and onions for a few minutes while aroma releases. Rinse 4 ounces sliced baby portobello mushrooms ahead of time, then add to skillet. Stir for a few minutes more then deglaze with 1 cup dry champagne.
Allow mushrooms, onions, and garlic to simmer for 5 minutes, then add 4 cups chicken stock and 2 cups heavy whipping cream. At this point, if you find your skillet isn’t big enough, transfer contents to a larger pot.
Keep liquids on a low simmer, stirring often and allowing not to burn. In a separate (preferably cast-iron) skillet heated on medium-high, add breakfast sausage mix and sear first side, then second, then break into small bits.
After liquids have simmered for 15 minutes, add ½ cup flour and mix in to thicken gravy while continuing to simmer. Lumps may appear, but as liquids continue to simmer, you can stir and use spatula to work out lumps.
After adding flour and mixing in thoroughly to thicken gravy, add fully cooked breakfast sausage.
Follow directions on biscuit can (or bake your own). When biscuits are finished, top with gravy. If gravy isn’t thick enough for your liking, sprinkle in 1 tablespoon of flour at a time, stirring in thoroughly before adding another tablespoon, until desired thickness is reached.