Clean the onion, carrot, garlic and celery. Saute them in butter and oil. Add all the tomatoes (fresh and canned), parsley, salt, tomato paste, black pepper, bay leaf, sugar and broth and leave to cook for 45 minutes over medium heat. Add starch by passing it through a puree machine and bring it to a boil and lower it from the fire. Then, serve it by mixing it with the spaghetti that you cook for the time indicated on the package.