Preheat your oven to 350°F and line an 8x8 inch baking pan with parchment paper, leaving an overhang for easy removal.
In a large bowl, mix together the butter and both sugars until combined. Add the egg and vanilla extract, and beat until well combined.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.
Press the dough evenly into the prepared pan. You can use your hands or a spatula to help spread it out. Sprinkle the chocolate chips on top and a garnish of granulated sugar.
Bake for 20 minutes, or until the edges are set and a toothpick inserted into the center comes out with a few moist crumbs.
Allow the bars to cool completely in the pan before slicing into squares.