Heat oil in a large saucepan over medium heat. Add onion and garlic and cook 3 to 5 minutes until softened, stirring frequently.
For a smoother soup, blend broth and cooked onion and garlic in a food processor or blender until very smooth; return to saucepan. Otherwise, proceed to Step 3.
Add broth if not used in Step 2, crushed tomatoes, tomato sauce and basil. Bring to a boil. Reduced heat to medium-low and simmer 5 to 7 minutes. Stir in cream. Heat over low heat about 1 minute, or until hot. Do not boil. Add sugar to taste, if desired. Serve with basil and garlic croutons, if desired.