Preheat the oven to 350℉. Line an 8×8-inch baking dish with parchment paper or grease lightly with butter. Set aside.

In a medium mixing bowl, whisk together the flour, baking powder, and salt, until combined. Set aside.

In a stand-up mixer fitted with the paddle attachment, mix together the melted butter and sugars on medium speed until smooth and creamy. Scrape down the sides of the bowl as needed, and mix in the vanilla.

Add the egg and mix until completely combined and the mixture has slightly lightened in color, about 30 seconds.

Turn the mixer down to low, and spoon in the flour mixture. Mix until just combined, scraping down the sides of the bowl with a spatula, as needed. Stir in 1/2 cup of the chocolate chips.

Turn the cookie dough out into the prepared baking pan, and use an offset spatula to even out the top and smooth the dough into the corners. The dough will be thick.

Sprinkle the remaining 1/4 cup of chocolate chips on top.

Bake for 18-22 minutes, until the bars look shiny and set, the edges are golden, and a cake tester inserted into the center comes out clean. Let the cookie bars cool in the pan before slicing. Serve warm.