Working in 2 batches, transfer vegetable mixture to a blender; add 2 cups of broth and half the cilantro and puree until very smooth, 30 seconds to a minute. Turn puree into a large pot; add coconut milk so that soup is thin enough to be soup, yet thick enough to float a garnish. Heat through, adjusting flavors, including additional salt and pepper. Ladle into bowls, garnish if you like*, and serve.