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.

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 the mixture is thick and glossy, and stiff peaks form.

Mix in the gel food coloring.

Add the sugar-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, I like to 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. (If the ‘8’ disappears quickly, you’ve overmixed!)

Transfer the batter to 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 the macaron 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 a few hours. I allowed this batch to rest for 2 1/2 hours.

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

Set aside to cool while you prepare the buttercream. (Once cool, the shells should fall from the silicone mat with almost no effort at all. If they stick, or if you find yourself peeling the shells away, you’ve underbaked.)

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. Add the gel food coloring and mix until smooth and creamy, about 3-5 minutes. (If necessary, add more confectioner’s sugar or milk to adjust the consistency. The buttercream should be smooth and creamy, yet firm enough to pipe.)

Transfer buttercream to a piping bag fitted with round or other decorative piping tip.

Assembly:

Pair the macaron shells according to size and shape.

Pipe a generous dollop of buttercream on the flat side of half of the shells.

Top with a second shell.

Store leftover macarons in an airtight container in the refrigerator for up to 5 days. Macarons can also be frozen in an airtight container for up to 3 months.