Heat oven to 375 degrees. In a bowl or stand mixer, beat butter, shortening, sugars, egg, and vanilla. Stir in dry ingredients, and mix well. Add chocolate chunks. Use a cookie scoop and scoop out cookie dough onto a cookie sheet. Bake for 8-9 minutes or mostly baked. Halfway through the baking process, bang the pan on the oven racks. This will cause the chocolate to run out onto the cookies. Remove cookies before they fully bake. They will keep baking outside of the oven. Cool on a wire rack.
