In a large mixing bowl cream together the butter, oil, and sugars until the mixture is fluffy. Add eggs, vanilla, and salt and mix until combined. With a wooden spoon, mix in the baking soda, cornstarch, Coffee, and flour. Stir in chocolate chips and cover and chill for 30 minutes.
Preheat oven to 350
After the dough has cooled in the fridge, form about 1 tablespoon of batter into balls and place on ungreased cookie sheets. For thicker cookies make sure the dough is nice and tall or you can stack two balls on-top of each other for extra thick cookies.
Bake 7-9 minutes depending on the size of the cookies. Remove from the oven when the edges are slightly golden and the centers look just barely done. Allow the cookies to cool for at least 5 minutes before eating.