Add butter and sugar to the bowl of a stand mixer (or a large bowl if you're using an electric hand mixer) and beat together until light and fluffy.

Add eggs to this butter/sugar mixture, one at a time. Add vanilla extract and mix until everything is well combined.

In a separate mixing bowl, whisk together the flours, cornstarch, baking soda, and salt.

Gradually add the flour mixture into the bowl of wet ingredients, one cup at a time. Mix on medium speed until you have a cohesive batter.

Cover the dough and chill in fridge for 30 minutes.

Divide the cookie dough and portion out evenly among 3 small bowls. Add a few drops of orange food coloring to one bowl, purple food coloring to another, and green food coloring to the third bowl. Knead each ball of dough until you have bright colors.

Take about a Tablespoon of each color of dough and mold together to form a ball. Press white chocolate chips into the surface of the cookie dough ball (we used about 8-10 per cookie). Repeat until all dough is used.

Place your Halloween sprinkles in a small bowl or shallow dish. Roll half of each cookie ball in the sprinkles. If needed, press the sprinkles into the dough so they stick. Place the cookie dough balls on your prepared pans and gently flatten, so that the cookies are about 1/2" thick.