Heat olive oil in 12-inch nonstick skillet over medium-high heat and cook onion, stirring occasionally, 3 minutes. Add garlic and cook 1 minute. Stir in 1 cup sauce and cook, stirring occasionally, 2 minutes or until thickened. Add shrimp and cook, stirring occasionally, 2 minutes or until shrimp turn pink. Stir in parsley. Cool, then stir in Mozzarella.