Penne with Italian Sausage and Peas - Serving Dumplings

Ingredients

• 12 ounces penne
• 1 tbsp olive oil
• 1 tbsp unsalted butter
• 14 ounces Italian sausage (casings removed)
• 1 small yellow onion (finely chopped)
• 4 garlic cloves (minced)
• 1 tsp salt
• 1 tsp black pepper
• 1 tsp dried basil
• ½ tsp chili flakes (more or less to taste)
• 14 ounces puréed tomatoes
• ½ cup grated Parmesan
• 1 cup frozen peas
• chopped parsley for serving (optional)