How to Make It
Preheat oven to 350°F. Line a 10- x 15-inch baking sheet with parchment paper; lightly coat parchment paper and sides of pan with 1 tablespoon of the butter.
Whisk together flour, baking powder, and salt in a medium bowl. Combine brown sugar, granulated sugar, and 1 cup butter in the bowl of a stand mixer, and beat on medium speed until soft and fluffy. Add eggs 1 at a time, and beat until incorporated. Stir in vanilla. Add flour mixture, and beat until just blended. Stir in chocolate chips.
Spread batter evenly into prepared baking sheet. Bake in preheated oven until lightly golden, 18 to 20 minutes. Serve warm, or let cool completely on a wire rack before decorating with icing, if desired.