Blacken ancho chile in heavy skillet over high heat until the colour darkens slightly and become fragrant, about 30 seconds. Transfer ancho chiles to medium bowl and add enough boiling water to cover. Let stand until softened, about 20 minutes. Remove from liquid and pull chile away from stem, cut into large pieces. Reserve ½ cup soaking liquid.
Char poblano chiles over a gas flame or under a broiler until blackened on all sides. Place in a plastic bag and steam for 10 minutes. Remove from bag, peel and seed chile. Cut chile into large pieces.
Puree ancho and poblano chiles with soaking liquid. Season with salt and pepper. (Can be prepared up to this point 1 day in advance.)
Add additional broth as needed to measure 3 cups total. Bring to a slow boil.
Reduce heat, sprinkle masa harina over the pan juices and whisk until mixture thickens, scraping up brown bits, about 2 minutes.
Add chile puree and simmer another 5 minutes to blend flavours. Taste and season with salt and pepper if needed. Serve with turkey and stuffing.