Salsa di Pomodoro - Tomato Sauce

1/2 cup extra-virgin olive oil
1 small onion, chopped
2 cloves garlic, chopped
1 stalk celery, chopped
1 carrot, chopped
Sea salt and freshly ground black pepper
2 (32-ounce) cans crushed tomatoes
4 to 6 basil leaves
2 dried bay leaves
4 tablespoons unsalted butter, optional

In a large casserole pot, heat oil over medium high heat. Add onion and garlic and saute until soft and translucent, about 2 minutes. Add celery and carrots and season with salt and pepper. Saute until all the vegetables are brown, about 7-8 minutes. Add tomatoes, basil, and bay leaves and simmer covered on low heat for 1 hour or until thick. Remove bay leaves and check for seasoning. If sauce still tastes acidic, add unsalted butter, 1 tablespoon at a time to round out the flavors.

Add half the tomato sauce into the bowl of a food processor. Process until smooth. Continue with remaining tomato sauce.