It's the sparkliest, prettiest, most dazzling dessert ever! It's a showstopper for any party and you can customize the colors and sprinkles you use to make it your own!
In a medium bowl, whisk together the heat-treated flour, cornstarch, cream of tartar, baking powder, baking soda and salt. Set aside.2.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until smooth and creamy, about 2 minutes. Add the sugar and mix on medium until light and fluffy; about 4 minutes will do the trick. Use a rubber spatula to scrape the bowl. Add the egg whites and vanilla and mix until fully incorporated, about 2 minutes.3.
Add half of the flour mixture and mix on low just until the powdery texture of the flour disappears, about 15 seconds. Immediately add the rest of the flour mixture and mix until combined. Scrape the bowl and mix a final 15 seconds.4.
Remove the bowl from the mixer and use a rubber spatula to fold in the sprinkles.5.
Once the sprinkles are well combined, make 3 small indentations in different places in the dough. I use my finger, but you can also use the back of a rubber spatula. Drop the food coloring in these indentations, one color per indentation.6.
Use a rubber spatula to swirl the food coloring into the dough. It should take only a few stirs to do this — too much stirring can make the dough gray (gray dough won't give you the magical moment you're looking for!). And like magic, you have dough that's ready to eat!