Carefully separate the egg yolks from the egg whites. (See notes for tips.) In the bowl of a stand mixer with a whisk attachment, whisk the egg whites on high speed until they form soft peaks (this usually takes between 10 to 15 minutes).
Sift in the powdered sugar and whisk for another couple minutes on medium speed, until the mixture is thick and creamy. It should look like a glaze or icing at this point.
Measure out ⅔ cup of the egg white mixture into a small bowl (this will be a good portion of the mixture). Cover the bowl tightly with plastic wrap and store in the fridge.
To your mixing bowl with the remaining egg white mixture, sift in the almond flour and cinnamon. Slowly mix by hand with a large spoon or spatula until it forms a dense but pliable dough.Cover the mixing bowl with plastic wrap and store in the fridge for 30 minutes.
Preheat the oven to 250°F. Move the oven rack to the lower third of your oven. Line a baking sheet with parchment paper.
On a clean work surface sprinkled with a little powdered sugar (not flour) roll out the dough until it’s ¼ to ⅓ inch thick. Cut out stars into the dough with a small star-shaped cookie cutter. Transfer the cut-out cookie dough to your prepared baking sheet.
Use the back of a spoon or a pastry brush to put a little of the reserved whipped egg whites from the fridge onto the top of each star. (See notes for tips.) You can smooth it out and pop any air bubbles with a toothpick.
Bake for 22 to 28 minutes, until the top is dry. Ideally you don't want the tops to turn golden, but rather stay a stark white. Allow the cookies to cool on the baking sheet for 10 minutes, then transfer them to a wire cooling rack to cool completely. Enjoy!!
Notes
Save the yolks from your separated eggs for another recipe like lemon curd or an omelet.
If your dough feels a little too wet or sticky, sift in a little more powdered sugar and mix again.
Be careful not to get any egg yolks mixed in with your egg whites. Any fat in your egg whites will make it way harder to whip them.
I always wipe my mixing bowl and whisk with a paper towel and a little white vinegar, which cleans out any butter or other fat that could be left on my equipment.
Egg whites separate easier when they’re cold, so do that right when they come out of the fridge. But they whip up fluffier when they’ve sat out at room temperature for 20 to 30 minutes. It's not necessary to leave them out, but if you have a little extra time, let them sit out before turning on your mixer.
For decorating, I find it easiest to dollop some meringue on a star and then use a pastry brush to brush the meringue to all the edges and points.
Try to work quickly as you decorate. As the meringue sits out at room temperature, it'll start to separate.