Preheat oven to 350°F.
In a small bowl, add the flour, baking soda and salt. Whisk, then set aside.
In the bowl of an electric mixer, cream together the butter and both sugars. Mix until fully incorporated.
While slowly mixing, add the vanilla, then egg and blend well.
While slowly mixing, pour in the flour mixture and blend just until fully combined. Add mini chocolate chips.
Scoop, then press the batter into a rectangular tart pan. Press up the sides, so the center is lower than the sides. Move batter filled pan to the fridge for 5 minutes so it's nice and firm and cool before baking.
Bake in preheated oven for 22-25 minutes. If the edges are getting too brown before the bottom is cooked, remove pan from oven and gently cover the edges with strips of foil to prevent further browning, then return to oven for a few minutes. The cookie is done when golden brown and puffed up.
Allow cookie to cool 3-5 minutes, then use a metal measuring cup or large metal spoon to press down the center of the cookie, creating a nice sized space for the caramel and chocolate filling to be added. Cool at least 20 minutes before adding caramel sauce.