Classic Stuffed Shells Recipe: Grandma's Secret!

Ingredients

• 1 (12-ounce) package jumbo pasta shells (about 30 shells)
• 2 tablespoons olive oil
• 1 medium onion, finely chopped
• 2 cloves garlic, minced
• 1 (28-ounce) can crushed tomatoes
• 1 (15-ounce) can tomato sauce
• 1 teaspoon dried oregano
• ½ teaspoon dried basil
• ½ teaspoon sugar
• Salt and freshly ground black pepper to taste
• 1 (15-ounce) container ricotta cheese, drained
• 1 (10-ounce) package frozen chopped spinach, thawed and squeezed dry
• 1 large egg, lightly beaten
• ½ cup grated Parmesan cheese
• ¼ cup chopped fresh parsley
• ¼ teaspoon ground nutmeg
• ½ cup grated mozzarella cheese