Pork Belly Pappardelle Pasta

Name: Pork Belly Pappardelle Pasta
Ingredients: 1 pound pork belly strips cut into a half inch dice; 1 cup finely diced onion (1 medium); 2 large cloves garlic, minced; 2 sprigs fresh rosemary; 1 teaspoon salt; 1/2 teaspoon black pepper; 1/4 to 1/2 teaspoon crushed red pepper flakes (optional); 1/2 cup dry white wine; 28 ounces canned whole San Marzano tomatoes; 3 cups chicken broth plus more if needed; 2 teaspoons minced fresh rosemary leaves plus a little more for garnish; 10 ounces pappardelle