Cream the butter and sugar together until light and fluffy. Beat in the egg and vanilla.
Whisk together the flour, cocoa powder, baking soda, salt and cornstarch. Stir into the wet ingredients. Gently stir in the pecans, chocolate chips and caramel bits. To make the cookies pretty reserve a few of the pecans, caramel bits and chocolate chips to press into the dough balls.
Chill the dough for at least 3 hours. Preheat the oven to 350 F. Roll the dough into 1 inch balls, press in extra pecans, caramel bits or chocolate chips if desired and bake for 9-11 minutes or until set. Do not over bake the cookies. They should like slightly doughy when they are taken out of the oven. Let cool on the cookie sheet for a few minutes and then remove to a wire rack to cool completely.