Preheat oven to 450 degrees F. Wash, core, and cut the tomatoes into halves. Spread the tomatoes, onions, and garlic onto a baking tray. (Add the cherry tomatoes, if using for garnish, leaving them whole and on the vine). Drizzle with the olive oil and season with salt and pepper. Roast for 20 to 30 minutes, until caramelized.

Remove cherry tomatoes on the vine and set aside for later use as a garnish. Transfer the remaining roasted tomatoes and the onions and garlic to a large stockpot. Pour in any roasting liquid from the tray, about 3 cups of the chicken broth, the bay leaves, and butter. Bring to a boil, reduce heat, and simmer for 15 to 20 minutes, until liquid has reduced by a third.

Remove and discard bay leaves. Add chopped basil leaves. Puree the soup with an immersion blender* until smooth. Return soup to low heat; add the 3/4 cup cream and adjust consistency with remaining chicken broth, if necessary. Season to taste with salt and pepper. Ladle soup into bowls. If you like, garnish each bowl with roasted cherry tomatoes and/or croutons.

If you do not own an immersion blender, you can puree soup in a regular blender in small batches. Add a small amount of soup to the blender, then hold the lid down tightly with a kitchen towel over the lid while blending. Be very careful; the steam can cause the lid to shoot off and the hot soup can burn you.