NYT Cooking: There are a few cool tricks to this recipe, one of which I picked up from an old issue of Bon Appétit, one I learned from Robb Walsh, the great Tex-Mex scholar and restaurateur who runs El Real Tex-Mex in Houston, and a final one I learned by happenstance. First, for the thickening agent in the chile sauce, toast raw all-purpose flour in a pan until it is nutty and golden brown, then reserve it...
