2 1/2cupscake flour, plus more for dusting work surface
1 1/2tspbaking powder
1/2cupsalted butter, at room temperature
1/4cupall vegetable shortening(unflavored), at room temperature
1large egg white
6Tbspsalted butter, at room temperature
food coloring, optional (I used Wilton red gel - for the red, and McCormick red liquid for the pink)
Sift flour, cornstarch, baking powder and salt into a large bowl, then whisk it just a few times, set aside. In the bowl of an electric stand mixer, on medium speed, whip together butter, shortening and sugar until very pale and fluffy, about 4 minutes, scrapping down the sides of the bowl as needed. Add in egg and mix until combine, then add egg white, vanilla and almond extract and mix until combine. With mixer running, slowly add in dry ingredients and mix just until combine. Shape dough into a ball and transfer to an airtight container and refrigerate 1 1/2 - 2 hours. Preheat oven to 375 during the last 10 minutes of refrigeration.
Remove dough from refrigerator and sprinkle a clean work surface and top of dough lightly with cake flour. Evenly roll dough out to 1/3-inch thickness (or up to 1/2-inch for thicker cookies, you just wont get as many). Cut into desired shapes (I used a medium heart cookie cutter and got 20 cookies). Transfer to Silpat or parchment paper lined baking sheets. Bake in preheated oven 8 - 11 minutes (cookies should NOT brown, they should remain a pale color). Remove from oven and allow to cool on baking sheet several minutes before transferring to wire rack to cool. Cool completely then frost with Vanilla Frosting and add sprinkles if desired (immediately after frosting each cookie so the sprinkles will stick before the frosting sets). Store in an airtight container at room temperature.
Combine all ingredients in a large mixing bowl, using an electric hand mixer, whip mixture on low speed until combine, then increase mixer to medium-high speed and whip until frosting is pale, smooth and fluffy.