Green Chile Tomatillo Soup

Roast and peel chiles (use either the stovetop method or broiler method). Remove papery skins from tomatillos. With the stove flame or oven broiler still on, roast the tomatillos until lightly blistered. Set aside until cool enough to handle and peel off as much of the skin as possible. In a medium pot, heat oil. Add onion and cook, stirring occasionally, until onions are soft, about 3 minutes. Add garlic and cook, stirring, until fragrant, about 1 minute. Add chiles, tomatillos, broth, salt, and potato, if using. Bring to a boil. Reduce heat and simmer 30 minutes to thoroughly cook vegetables and blend flavors. Whirl, in batches, if necessary, in a blender or food processor until very smooth (you can also use a hand-held blender if you have one). Add cream, if using. Add more salt to taste. Serve hot, garnished with cilantro, if you like.