Preheat the oven to 350°F. Line a 9-inch square baking pan with parchment paper then grease the parchment.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, white sugar and brown sugar until light and fluffy, about 2 minutes.
Beat in the egg and vanilla extract.
Add the flour, baking soda, baking powder and salt, and beat just until combined, scraping down the sides of the bowl as needed.
Beat in the chocolate chips.
Spread the cookie dough into an even layer in the prepared baking pan.
Bake until pale golden, 17 to 20 minutes. Remove the pan from the oven and, while the cookie is still warm, use a sharp knife or the edge of a spatula to score it into 1-inch squares. Let cool completely in the pan, then cut along the scored lines to separate the cookie croutons.