Rustic Italian Soup

Ingredients

• 3/4 pound Italian turkey sausage links, casings removed
• 1 medium onion, chopped
• 6 cloves garlic, minced
• 2 (14.5-ounce) cans reduced-sodium chicken broth
• 1 3/4 cups water
• 1 (14.5-ounce) can diced tomatoes, undrained
• 1 (9-ounce) package refrigerated cheese tortellini or pasta shells
• 1 (6-ounce) package fresh baby spinach, coarsely chopped
• 2 1/4 teaspoons fresh basil, minced or 3/4 teaspoon dried basil
• 1/4 teaspoon pepper
• crushed red pepper flakes, to taste
• parmesan cheese, optional, shredded, and to taste