Preheat oven to 350°F. Line an 8″x8″ baking dish with parchment paper and set aside.
In a standing mixer fitted with a paddle attachment, cream butter and sugar until light and fluffy, about 3 minutes. Add in egg and vanilla during last minute of mixing. Turn mixer speed to low and mix in flour, baking soda, and salt until just combined. Remove from standing mixer and fold in chocolate chips.
Place dough into baking dish and smooth using the back of a spatula. Bake for 30 minutes, or until the top is golden brown and a knife inserted in the center of the dough comes out mostly clean. Allow to cool for 20 minutes before removing from pan and cutting into 9 squares!