Chill butter and sugars in the refrigerator
Using a stand mixer, beat the cold butter, butter flavored Crisco, brown sugar, and white sugar until it reaches a wet sand consistency
Add eggs and vanilla to the mixture
Increase mixer speed and beat until well combined, scraping down the sides at least once
In a separate bowl, combine flour, baking soda, salt, and corn starch
Add the dry ingredients to the wet mixture on low speed at a slow, consistent rate until just combined
Fold in dark chocolate chips
Form into large or average-sized portions on baking sheet
Bake at 350°F for 12-15 minutes for large cookies or 8-10 minutes for average size
