Heat a large nonstick saucepan over medium-high heat. Add sausage; sauté 4 minutes or until browned. Combine milk and flour in a small bowl, stirring well with a whisk. Add milk mixture to pan; bring to a boil, stirring constantly. Reduce heat to medium. Stir in cheeses, onion powder, and garlic salt; cook 3 minutes or until cheeses melt, stirring constantly. Stir in pasta. Garnish with parsley, if desired. Serve immediately.