Heat the olive oil in a 4 1/2 quart Dutch oven or soup pot over medium heat. Peel and finely chop the onion and add it to the pot. Stir and cook for 2 minutes. Meanwhile, open the tomato and sauce cans.
Add the garlic, and stir and cook for 30 seconds. Add the tomatoes with their juices and the tomato sauce. Raise the heat to high, and bring the soup to a boil.
Reduce the heat to low. Stir in the milk and parmesan cheese. Do not boil the soup after the milk has been added. Stir and cook for 2 minutes. Remove from the heat and serve at once. Garnish with croutons and fresh snipped herbs.
NOTE: Use the Del Monte brand of diced tomatoes seasoned with basil, garlic and oregano. If you can't find the seasoned tomatoes, add 1/2 teaspoon each dried basil and dried oregano with plain diced tomatoes.