For the Sauce:

• 2 tablespoons olive oil
• 1 large onion, finely diced
• 6 cloves garlic, minced
• 1/2 teaspoon red pepper flakes
• 1 pound 85% lean ground beef
• 1 pound Italian sausage, sweet or spicy
• 3 tablespoons tomato paste
• 1/2 cup red wine or beef broth
• 2 teaspoons Italian seasoning
• 2 28-ounce cans crushed tomatoes
• 1/2 teaspoon salt, more to taste
• 1/4 teaspoon ground black pepper, more to taste
• 2 teaspoons granulated sugar
• 1/2 cup fresh basil, chopped
• 3 tablespoons fresh parsley, chopped

For the Ricotta Mixture:

• 15 ounces ricotta cheese
• 1/2 cup parmesan cheese, finely grated
• 5 ounces fontina cheese, coarsely grated
• 1 large egg
• 1 large egg yolk
• 2 tablespoons parsley, finely chopped
• 2 tablespoons basil, finely chopped
• 1/8 teaspoon salt
• 1/8 teaspoon freshly ground black pepper

For the Baked Ziti:

• 1 pound ziti noodles or penne
• 4 ounces low-moisture mozzarella cheese, finely shredded
• 4 ounces fontina cheese, cut into 1/4-inch cubes
• 1 tablespoon fresh parsley, finely chopped (for serving)