Preheat oven to 350. Spray an 8-inch square pan with non-stick cooking spray.
Whisk flour and baking powder together in a small bowl; set aside. In a separate bowl, whisk cocoa, water, vanilla and espresso powder together until smooth; set aside.
Microwave butter and chocolate chips together on 50% power until melted, about 1 minute; whisk until mixture is smooth. Whisk in sugar and salt until completely incorporated. Add the cocoa mixture and whisk until smooth; whisk in the egg. Stir in the flour mixture until just incorporated (do not over-mix).
Pour batter into prepared pan and smooth top. Bake until toothpick inserted into center comes out with a few moist crumbs attached, 20-25 minutes, rotating the pan halfway through baking. Cool completely on a wire rack; remove from pan and cut into 9 or 12 brownies.