Makes about 2 pints
1. Heat a charcoal grill or turn on the broiler. Over a hot grill or under the broiler, roast the bell peppers and serrano pepper, turning often, until they are charred all over. When the skins are blackened and the peppers are soft, transfer them to a bowl. Lightly cover with plastic wrap; set aside until cool enough to handle. Transfer the peppers to a cutting board; reserve any juices that accumulate in the bowl.