Source  Brown Eyed Baker

Recipe Added:  1/9/2015

Preheat oven to 325. Grease 9" round cake pan, then line the bottom with parchment paper; set aside. Whisk flour, baking powder, baking soda, and salt together in a medium bowl; set aside. Using an electric mixer on medium speed, beat butter and sugars until thoroughly blended. Beat in 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 dough out into the prepared cake pan and press into an even layer. Bake until cake is light golden brown and outer edges have started to harden, 20-25 minutes. Remove from oven and cool completely on a wire rack. Use a metal spatula to loosen sides of the cake from pan, then turn out onto a serving plate. Serve or decorate as desired. Leftovers should be wrapped in plastic wrap and kept at room temperature for up to 5 days.

1. http://www.browneyedbaker.com/chocolate-chip-cookie-cake/