In either a stand or hand-held electric mixer, cream the butter and sugar until light and soft, about 3 minutes. Add the egg, vanilla and orange zest and mix to combine.
In a separate bowl, whisk together all dry ingredients - flour, cocoa powder, baking powder and salt. Add to the butter-sugar-egg mixture and beat until just combined.
Add the chocolate chips and fold in with a spoon. (I waited until all the cookies were on baking sheets and individually placed five chocolate chips in each one, but in retrospect that seems awfully fussy.)
Plop teaspoon-sized balls on a greased cookie sheet and bake at 350 degrees for roughly 10 minutes. Remove from tray and cool on a wire rack, or, as my mother always does, on a brown paper grocery bag.