Place a heatproof bowl over a small pot of simmering water. 

Add the egg whites and granulated sugar to the bowl and constantly whisk until the sugar has fully dissolved, about 2 minutes. 

Transfer the egg whites to the bowl of a stand mixer fitted with the whisk attachment. 

Whisk on medium speed until the egg whites form stiff peaks, about 4 minutes. Don’t rush this step. Just keep mixing at medium speed and eventually, the peaks will form. 

Once the egg whites have formed stiff peaks, place a fine mesh sieve over the mixing bowl and add the powdered sugar and almond flour. 

Sift half of the dry ingredients into the egg whites.

Then, carefully fold the dry ingredients into the egg whites by making a J shape with your spatula. Gently fold (about 25 folds) the dry ingredients until no large lumps remain. 

Then, add the second half of the dry ingredients. 

Continue folding until the meringue reaches the lava stage, about 1-2 minutes of folding. 

You’ll know the meringue is ready to pipe when you can draw a figure 8 without the stream breaking. 

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

Pipe 1-inch circles and pipe them at least 1.5 inches apart on a parchment or silpat-lined baking sheet. 

After you’ve piped a full tray, hold it 6 inches off the counter and drop it straight down to release any air bubbles. Repeat 4-5 times, or until it looks like any large air bubbles have popped. 

Set the macarons aside to dry at room temperature for 30 minutes, or until they develop a skin. While the macarons rest, preheat your oven to 325 degrees F. 

Bake the dried macarons in a fully preheated oven for 12-14 minutes, or until they are just starting to turn golden brown around the edges. 

Remove the macarons from the oven and allow them to cool fully on the tray. 

Once the macarons have cooled, place them in similar-sized pairs and continue with the filling below. 

Add the butter to the bowl of a stand mixer fitted with the paddle attachment. 

With the mixer on low, slowly add in the powdered sugar a little at a time. 

When the powdered sugar is all incorporated, add the pumpkin spice and vanilla. 

Turn the mixer to medium-high speed and beat until the icing is smooth and fluffy. 

Transfer the filling to a piping bag fitted with your choice of tip. 

Pipe a small dollop of filling onto the center of one of the macaron shells and place the other macaron shell on top. Repeat with the remaining macarons. 

Transfer the macarons to an airtight container and place them in the fridge to age overnight. 

Bring the macarons to room temperature before serving. Store in an airtight container in the fridge for up to three days.