Preheat oven to 350ºF. Slice into the side of each chicken breast to create a pocket.
Sauté garlic and mushrooms in 1 tablespoon oil. Add Marsala and simmer until mushrooms have absorbed the wine. Set aside to cool.
Add bread crumbs, spinach, green onions, basil, Parmesan, salt and pepper to the cooled mushrooms. Mix in sausage until everything is incorporated.
Open the chicken breast pockets and fill with the stuffing. Dredge in seasoned flour and sauté in olive oil over medium heat until lightly browned. Finish cooking in the oven for 15 minutes, or until chicken is firm to the touch and has an internal temperature of 160ºF.
Serve with a Marsala sauce or tomato sauce. This is also good served without a sauce if you so desire. Makes 6 servings.
*Brands may vary by region; substitute a similar product.