Simple Bolognese

The recipe:

1/4 cup extra virgin-olive oil
1 medium onion, minced (food processor)
3 garlic cloves, minced (food processor)
1 celery stalk, minced (food processor)
1 carrot, minced (food processor)
1/2 to 1 lb ground beef (ground round)
1 28 oz can crushed San Marzano tomatoes (found at Whole Foods)
1/4 cup fresh flat-leaf parsley
1/2 tsp salt, plus more to taste
1/2 tsp pepper, plus more to taste
1/4 cup freshly grated Parmesan

Heat the oil in dutch oven. Add onion and garlic and cook until tender. Add celery and carrot and cook another 5 minutes. Increase heat to high, add beef, and cook until no longer pink. Add tomatoes, parsley, 1/2 tsp each of salt and pepper and cook until sauce thickens, about 30 min.
Stir in cheese and season with more salt and pepper to taste. Serves 4.