Macaron Shells:

Line a half-sheet rimmed baking tray with parchment or a silicone mat.

Sift the confectioner’s sugar into a medium bowl, using a bench scraper to help push the sugar through the sieve. Discard any clumps or hard bits of sugar. Sift the almond flour into the same bowl. Discard any large clumps or pieces. Set aside.

Add the egg whites to a large mixing bowl or the bowl of a stand mixer. Mix on high speed until soft peaks form. Gradually add the caster sugar, continuing to mix on medium-high speed until thick and glossy, and stiff peaks form.

Mix in the blue gel food coloring.

Add the sugar and almond flour mixture to the bowl. With a rubber spatula, fold the dry ingredients into the meringue. At first, the batter will feel very thick and dry.

Continue folding, gradually deflating air from the mixture, until the batter flows from the spatula like lava. To test whether the batter is ready to pipe, make a figure ‘8’ shape with the batter—it should take about 8-10 seconds to sink back into the bowl. If it takes longer than this, it’s too thick. Test frequently to avoid overmixing the batter.

Scoop batter into a piping bag fitted with a 5/8-inch round piping tip.

Pipe 1 1/2-inch rounds onto prepared tray, allowing a few inches of space between the rounds. Firmly tap the tray on a table or countertop to remove the air bubbles. (If any bubbles remain, gently pop them with a toothpick/cocktail stick.)

Set aside and allow shells to rest, uncovered, at room temperature until dry to the touch. Depending on the temperature and humidity in your kitchen, this can happen in as little as 30 minutes, or it might take up to 3-4 hours.

Preheat oven to 140° C / 285° F. Bake for approximately 20-25 minutes, or until the shells no longer “dance” (jiggle) on their feet when touched.

Remove from the silicone baking mat and pair by size.

(Note: These are the temperatures and timings that work best for me, but all ovens are different. If you have a “tried and true” temperature and bake time for making macarons, definitely use that instead! If not, try mine and adjust as necessary. I suggest checking the macarons every few minutes, beginning at the 15-minute mark.)

Buttercream:

In a large mixing bowl or the bowl of a stand mixer, whip the softened butter on high speed until light and fluffy. Gradually add the confectioner’s sugar, alternating with the milk and mixing well after each addition. If necessary, add more confectioner’s sugar or milk to adjust the consistency.

Scoop half of the buttercream into a small bowl. Mix in red gel food coloring.

Transfer each color to a separate disposable piping bag. Use kitchen shears to snip the corners.

Unroll a piece of clingfilm/plastic wrap, about 16-18 inches long. Pipe alternating stripes of each color on top of the plastic.

Gently roll the clingfilm around the buttercream, forming a tube. Cut the tube in half.**

Place one half of the tube, cut side facing down, inside a larger piping bag fitted with a star, French star, or other piping tip of choice.

Pipe a generous swirl on flat side of half of the shells. Top with remaining shells.

Melt the cocoa butter according to manufacturer’s instructions. With a food safe paintbrush, brush the tops of the shells with cocoa butter.

Sprinkle with foil stars and dust with edible glitter.

Store leftover macarons in the refrigerator for up to 5 days, or freeze for up to 3 months.