Preheat oven to 350°F.
Cream butter and sugars together until light and fluffy, about 2 minutes.
Add egg, vanilla, and food coloring, and mix until thoroughly combined.
Sift together flour, cocoa powder, cornstarch, baking soda, and salt and add to butter and egg mixture ⅓ at a time.
Mix together until just combined.
Add white chocolate chips, and mix in by hand.
Portion the dough into 8 equal balls of dough.
Bake for 9-11 minutes, or until the cookie tops are just about to set.
Remove and let cool before storing in an airtight container.