Roast the eggplant, bell peppers, and tomatoes by holding them over an open flame (or broil them) so that they are black all over. Remove the skins. Remove the seeds from the bell peppers and the tomatoes. Chop the eggplant, bell peppers, and tomatoes. Set them aside.
In a medium large saucepan place the olive oil and heat it on medium high until it is hot. Add the onions and saute them for 3 to 4 minutes, or until they are tender.
Add the roasted eggplant, bell peppers, and tomatoes. Stir the ingredients together. Add the garlic, cumin, and chicken stock. Simmer ingredients for 45 minutes. Add the cream and stir it in.
Pour the soup into a blender and puree it so that it is smooth. Season the soup with the salt. Garnish it with the sliced basil.