Preheat the oven to 350F. Line an 8 inch square metal pan with nonstick foil.
Melt the butter and chocolate together in the top of a double boiler, stirring often until melted and smooth. Remove from heat and let cool slightly.
Beat eggs on high speed of an electric mixer. Gradually add sugar and vanilla, beating 3 minutes or until thick and pale.
With a heavy duty scraper, fold in the chocolate mixture until blended.
Thoroughly whisk the flour, salt, baking powder and ancho powder together in a separate bowl, then stir the flour mixture into the chocolate mixture. Make sure the batter is not so warm that it will melt the chocolate chips, then stir in chips.
Pour into the pan and bake on center rack at at 350° for 25 to 30 minutes. They're done when a meat thermometer inserted in the center registers 210. Let cool in a pan set on a wire rack for about an hour, then transfer to refrigerator and chill for another hour or two or until very cold.
Lift foil with brownies out of pan. Cut brownies into 4 Texas size squares. You can then wrap the four squares or cut each square into smaller servings.