Step 1

Preheat the oven to 350°F. Line baking sheets with parchment paper or silicone baking mats. Set aside.

Step 2

Sift dry ingredients. Sift the cake flour and baking powder into a medium bowl and whisk a few times.

Step 3

In a measuring cup or small bowl, whisk together the egg whites, cream, and vanilla extract until well combined.

Step 4

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and granulated sugar on medium speed until the mixture looks pale, creamy, and fluffy, about 5 to 6 minutes.

Step 5

With the mixer running, add the egg white-cream mixture in multiple additions until combined. Using a rubber spatula, scrape down the sides of the mixing bowl halfway through. Decrease the speed to low and add the cake flour mixture. Keep mixing until a soft dough forms and there are no more streaks of flour.

Step 6

Using a 2 tablespoon, or #40, cookie scoop, drop portions of dough onto the prepared baking sheets. Leave 2 inches between each dough ball as it spreads a bit.

Step 7

Bake the cookies in the preheated oven for 12 to 15 minutes. The cookies should look puffy, pale, and barely golden around the edges. Let the cookies cool completely on the baking sheet before frosting.

Step 8

Store them in a single layer in an airtight container if you will frost them later. The container helps to seal in the moisture.

Step 9

Add the softened butter, powdered sugar, heavy cream, and vanilla extract to the bowl of a stand mixer fitted with the whisk attachment. Start mixing on low speed to incorporate the powdered sugar. Continue mixing for 2 to 3 minutes on high speed until the frosting is light and fluffy. Stop the mixer and scrape the sides of the mixing bowl down. Continue mixing.

Step 10

Frost the cookies when cool and decorate them with sprinkles. The frosting sets quickly, so add sprinkles immediately after icing a cookie.

Step 11

Store the cookies in a single layer in an airtight container. They will last for up to 5 days at room temperature. If you must stack them, let the frosting set and place waxed paper between layers of cookies.