Prepare a macaron template by using a large piping tip or small round cookie cutter of about 1 ½" in size to trace circles about 2 inches apart on one sheet of parchment paper. You will place this under another piece of parchment paper when ready to pipe the macaron shells.

In a medium bowl, sift the powdered sugar and almond flour twice.

Next, heat the egg whites and granulated sugar over a double boiler until the sugar has dissolved or until the temperature is about 120 degrees F.

Transfer the egg white mixture to a large bowl or a bowl of a stand mixer fitted with a whisk attachment. Whisk on medium speed until the meringue reaches soft peaks. At this point, you can add the vanilla.

Continue whisking the meringue until stiff peaks form. A good way to test if it is ready is by turning the bowl upside down. If the meringue does not fall or move at all, then it is ready.

Once the meringue is ready, start by folding in ⅓ of the dry ingredients. Mix carefully with a rubber spatula by scraping the sides of bowl, then through the middle of the mixture. Do this a few times until it is mostly combined.

Add the remainder of the dry ingredients, folding with the same gentle method. Once the dry ingredients are fully incorporated, begin gently spreading the mixture on the sides of the bowl to deflate it slightly. I find that this mixing method ensures that the shells do not bake up hollow. Continue scraping around the sides of the bowl and through the middle. The mixture is ready when you can draw several figure eights without breaking.

Transfer the mixture to a piping bag with a small round pipping tip (I used Ateco 802). With the macaron template placed under the parchment paper on the baking sheet, pipe at a perpendicular angle to fill in the circles. Carefully remove the template and tap the baking sheet on the counter a few times in order to release any air bubbles. It also helps to bang on the bottom of the baking sheet with your hand.

Immediately, top each with nonpareil rainbow sprinkles.

Let the macarons rest for about 30-40 mintues, or until they are dry and no batter comes away when you touch them.

Toward the end of the resting time, preheat the oven to 300 degrees F.

Bake the macarons for about 12 minutes. Allow to cool completely before removing them from the baking sheet.

In the bowl of a stand mixer fitted with a whisk attachment, combine the heavy cream, cream cheese, mascarpone, sugar, vanilla, and salt.

Whisk on low speed until fully combined, then turn up to medium high speed until thick (only about 30 seconds).

Transfer the frosting to a piping bag fitted with a small round tip.

Pair the macaron shells up and pipe the frosting onto the bottom shell, then place the paired shell on top, pressing down slightly to ensure they stick together.