Preheat oven to 400 degrees and prep a baking sheet with parchment paper.
Melt butter in a large skillet.
Brown breakfast sausage (12 ounces) in a large skillet over medium heat, and break up with a wooden spoon while it cooks.
Remove sausage from the skillet and place it on a paper towel lined plate.
Use a paper towel to clean the skillet of sausage grease.
Melt butter in the skillet.
Add onions (1 large finely chopped), carrots (2 finely chopped) and celery stalks (4 finely chopped). Sprinkle with salt (1 teaspoon) and pepper (1/2 teaspoon). Cook in butter until they're soft and lightly browned (around 10 minutes).
Add wine (1/2 cup) to skillet and bring to a boil. Cook until no wine is left — about 5 minutes.
Add finely chopped fresh parsley (1/4 cup), sage (1 tablespoon), thyme (1 tablespoon), and salt (1 ½ teaspoons). Stir to combine.
Create a pocket in each of your chicken breasts (6 breasts) using a knife.
Stuff each pocket with stuffing and a few spoonfuls of parmesan cheese.
Place the chicken breasts on prepared baking sheet and into the oven. Cook for 35 minutes, or until the center of the thickest piece of chicken is no longer pink.
Sprinkle with fresh parsley and enjoy!