1
In a large stock pot, heat the oil and garlic over medium heat. Toast until golden. Add the chile flakes and toast for 1 minute. Add the onion, celery, carrots, salt and pepper and cook until fragrant and soft.
2
Add the sausage and cook until brown, breaking it into smaller pieces. Drain out the excess fat.
3
Add the crushed and diced tomatoes and bring to a boil. Simmer for 10-15 minutes, until flavorful, stirring regularly. Adjust the seasoning to taste.
4
Meanwhite, bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions. Drain the pasta, return to the pot, and drizzle with olive oil to prevent sticking.
5
Combine all of the pesto ingredients except the oil in a blender, food processor, or immersion blender. Process until mostly smooth. With the motor running, slowly add the oil until you reach a smooth and creamy consistency. Season to taste.
6
Toss the pasta with the ragu and divide between plates. Drizzle with pesto and parmesan to serve.