Preheat the oven to 350°F.

Line 4 cookie sheets with parchment paper.

Combine the egg whites, heavy cream, and vanilla extract in a small bowl. Whisk well and set aside.

In the bowl of a stand mixer, combine the butter, sugar, baking powder, and salt. Using a paddle attachment, cream everything together on medium speed until it is nice and fluffy. This will take approximately five minutes.
Scrape the bowl about halfway through, to ensure even mixing.

Add the egg white mixture to the butter mixture in four or five additions, beating after each addition, until smooth and creamy.

Remove the bowl from the stand mixer. Add the cake flour, then fold and mix until a smooth, soft dough is formed.
At first, the mixture will be dry and lumpy. Keep the faith and keep gently mixing! Eventually, the dough will become much smoother and softer. It will look like a very thick cake batter.

Bake the cookies for about 15 minutes. Rotate the cookie sheets halfway through baking.
Allow the cookies to cool completely before frosting.

Shown below, you can see that the cookies should be very lightly browned on their bottoms. Their internal texture is light and fine.

Play the freeze dried fruit in to sealed plastic bags. Crush the fruit thoroughly with a rolling pin until it is very fine dust.

Pass the dried fruit through a fine sieve to eliminate any seeds or chunks.

Add the butter, powdered sugar, the vanilla extract, and the salt to the bowl of a stand mixer. Beat on medium speed until everything is light and creamy (approximately five minutes).

Transfer about half of the frosting to a separate bowl.

Add the crushed freeze-dried blueberries to one batch of frosting and cream well.

Use the back of a spoon to apply the frosting liberally onto each cookie. Then, add sprinkles!

Repeat the process with the raspberry batch.

Notes:
♥️ Since I wanted a more intense purplish-blue color, I did add some gel food coloring to the blueberry frosting batch.