Preheat oven to 350 degrees. Grease a 9 x 9 pan with non stick cooking spray, set aside.

In a stand mixer with the paddle attachment add butter and sugar and beat until creamy.

Add in egg and vanilla and beat until combined, scraping down the sides of the bowl.

In a medium bowl combine the salt, baking soda and flour.

Add the dry ingredients to the stand mixer on low just until combined. Make sure not to overmix.

Fold in the chocolate chips.

Press 2/3 of the dough into the prepared pan. Set aside while you prepare the fudge.

Spread the fudge ontop of the cookie dough in an even layer.

Layer with the remaining cookie dough. (I flatten the dough between my hands and lay it ontop. It is fine if it does not cover the whole pan.)

Bake for 25 minutes or until golden brown and the edges start to pull away from the sides of the pan.

Allow it to cool completely before cutting. I place mine in the fridge for a couple hours to make it easier to cut.

Add the condensed milk and chocolate chips to a small saucepan. Over medium low heat stir until melted and smooth.