Preheat the oven to 400 degrees.

In a large mixing bowl, cream together the butter, brown sugar, and sugar. Mix for 1-2 minutes.

Add in the eggs and vanilla and mix for an additional minute.

Stir in the flour, cornstarch, baking soda, and salt and mix until just combined.

Fold in the chocolate chips and chopped chocolate bar.

Using a large 3 tablespoon cookie scoop, scoop the dough onto a large cookie sheet leaving 3 inches in between each cookie.

Bake for 10-12 minutes or until the cookies just look set. Remove from the oven and cool on the baking sheet for 8-10 minutes before removing to cool completely on a wire cooling rack.