Melt the butter and let it cool. Beat the eggs. Sift the dry ingredients (flour, baking powder, cocoa) together for even mixing.
Attach the kneading blades. Add ingredients to the baking pan in the recommended order (usually liquids first, then dry, with sugar/salt in between; check your manual). Avoid adding chocolate chips yet.
Place the pan in the machine, close the lid, select CAKE course (Course 13), and set crust to MEDIUM. Press START.
When the "add" beep sounds (partway through), open the lid and scrape down any flour on the sides with a rubber spatula. Add chocolate chips/nuts. Close the lid and press START to resume (if needed). Be careful around moving blades.
When the cycle completes (typically ~1 hour 50 min–2+ hours on CAKE), press CANCEL, remove the pan, and let the brownies cool in the pan for 10–15 minutes before turning out onto a rack. Cool completely before slicing.