Preheat oven to 325 degrees F. Grease a 9-inch round cake pan, then line the bottom with a round of parchment paper; set aside.
Whisk the flour, baking powder, baking soda, and salt together in a medium bowl; set aside.
Using an electric mixer on medium speed, beat the butter and sugars together until thoroughly blended. Beat in the egg, yolk, and vanilla until combined. Add the dry ingredients and beat at low speed just until combined. Using a rubber spatula, stir in the chocolate chips.
Turn the dough out into the prepared cake pan and use your fingers to press into an even layer. Bake until the cookie cake is light golden brown and the outer edges have started to harden, 20 to 25 minutes. Remove from the oven and plan the pan on a wire rack to cool completely. Use a metal spatula to loosen the sides of the cake from pan, then turn it out and place it on a serving plate or platter. Serve or decorate as desired. Leftovers should be kept in an airtight container and kept at room temperature for up to 5 days.