Mostaccioli

Name: Mostaccioli
Prep time: 20 min
Cook time: 40 min
Total time: 1 h
Cuisine: Italian
Ingredients: 2 Tablespoons olive oil; 1 yellow onion (medium, finely diced); 1 Teaspoon kosher salt; ½ Teaspoon black pepper (freshly ground); 3 Cloves garlic (minced); 1 Pound sweet Italian sausage (ground); ¼ Teaspoon crushed red pepper flakes (optional); 24 Ounces marinara sauce; 16 Ounces mostaccioli pasta; 15 Ounces ricotta cheese (whole milk ricotta); 1 egg (large); ½ Cup + 3 Tablespoons parmesan cheese (freshly grated); 2 Cups mozzarella cheese (part-skim, freshly shredded); fresh basil leaves (for garnish)