Preheat oven to 350˚F.
Whisk together the flours, baking soda, and salt.
In a separate mixing bowl, cream together the butter and sugars until mixture is light and fluffy (about 2 minutes). Add in the egg and vanilla. Mix until fully incorporated.
Slowly add the flour mixture to the wet ingredients and beat until just combined. Fold in the chocolate chips.
Transfer dough to a 12-inch ovenproof cast iron skillet. Press the dough into the skillet until flat.
Bake in the preheated oven for around 20-25 minutes, or until the edges are golden brown. Do not over bake. It will continue to cook a few minutes out of the oven. Transfer to a wire rack to cool in pan.