How to Make It
In large nonstick skillet, brown sausage over medium-high heat. Stir in onion, spinach and mushrooms. Cook, stirring occasionally, 5 minutes or until sausage is done. Stir in sauce; heat through.
For each sandwich, split open each bread piece, and evenly spoon in sausage mixture. Sprinkle, if desired, with crushed red pepper flakes.