This sauce recipe from the Chicago Tribune is adapted from Petra Gutierrez de Romero, whose family operates a stall in La Merced market, selling chilies and other dried goods. She has worked in the market for 30 years, and also worked as a cook for 17 years. Serve this with warm tortillas. If you can't find all the varieties of the chiles, then use what you have but it is wonderful how much more available various dried chiles are than they were in the past. This is labor intensive, but it will be a labor of love--the dish is truly worth the effort.