In a large bowl with an electric mixer, beat together the butter and sugars until fluffy. Add in the egg and vanilla and stir.
In a separate bowl whisk together the flour, baking soda, salt, and cornstarch. Stir into the wet ingredients and fold in the chocolate chips.
Place a piece of parchment paper into the slow cooker, making sure to cover the bottom and a bit up the sides. Spread the dough onto the paper evenly.
Cook on high until cooked, about 2-3 hours. Turn off slow cooker and let sit 15 minutes to cool. Remove from slow cooker and cut into squares.
Add nuts to make this cookie a bit nutty.
To prevent a soggy top, place a few pieces of paper towel beneath the lid to catch the condensation.
Serve these Chocolate Chip Cookie Bars with a Pomegranate Smoothie.