Over medium heat, combine the butter and olive oil. Add the onion, carrots and garlic and season with salt, pepper and the dried basil. Cook until the onions are tender. (It's ok if the carrots are not completely tender).
2 tablespoons butter, 2 tablespoon olive oil, 1 medium onion, 2 large carrots, 1 teaspoon dried basil, Salt and Pepper, 1 large clove garlic
Add the diced tomatoes, chicken stock and sugar. Stir to combine.
29 oz cans diced tomatoes, 32 oz chicken stock, 4 tablespoons sugar
Cover and turn the heat to high. Bring to a boil for 5 minutes.
Reduce the heat and simmer for 20 minutes.
Puree the soup using an immersion blender. Add the cream just before serving.