Preheat oven to 375 degrees F. In a medium bowl, mix together the flour, cocoa powder, cornstarch, baking soda and salt. Set aside.
Add butter, shortening and sugar to the bowl of an electric stand mixer and mix on medium speed until very fluffy, about 3 or so minutes. Add egg, egg yolk and mix until combined. Then add vinegar, vanilla and food coloring. Mix until well blended.
Slowly add dry ingredients and mix until just combined. Stir in 1/2 cup white chocolate chips. Scoop dough out by the heaping Tablespoonful, and roll into balls. Place balls on a parchment lined baking sheet. Gently press about 4-5 more white chocolate chips into the top of each ball. Being careful not to flatten the balls.
Bake cookies for 8-9 minutes. Allow cookies to cool for a few minutes before transferring to a wire rack.