Preheat the oven to 400 ˚F
Place the peppers on a baking sheet and brush with olive oil.
Place the peppers in the oven on the top rack until they are black on all sides. About 30 minutes.
Take out of the oven, put the peppers in a paper bag and let stand 10 minutes. Peel, seed and slice the peppers.
Heat the oil in a large saucepan over medium heat. Add the onion, garlic and thyme and sauté 3 minutes. Add 3 cups of broth and all the remaining ingredients. Simmer, uncovered for 20 minutes.
Puree the soup in a blender until smooth. Return to the same pot. Add the cream, vinegar and cayenne pepper. Reheat the soup, thinning with additional broth, if desired.
Season to taste with salt and pepper. Pour the soup into bowls.
Garnish with crackers and basil if desired.