Preheat your oven to a low 200°F (93°C). Line two baking sheets with parchment paper to ensure your delightful cookies don't stick.
Carefully separate 4 large eggs, putting the whites into a sparkling clean mixing bowl. It's easy, just make sure no yolk sneaks in!
Beat the egg whites on medium speed until they're light, airy, and wonderfully foamy. Add the cream of tartar and continue beating until you start seeing soft, cloud-like peaks form – this is your meringue base!
While your mixer is still running, gradually add the granulated sugar, one tablespoon at a time. This slow addition is key for a super glossy, thick meringue. Pop in a pinch of salt with your last spoon of sugar.
Keep beating until the meringue is super shiny, thick, and holds firm, stiff peaks when you lift the beater. Stir in your chosen extract (vanilla or peppermint) briefly to blend the flavors.
Carefully fold in the green food coloring. Mix just enough to get an even, festive green without squishing the air out of your beautiful meringue.
Transfer the colorful meringue to a piping bag. Pipe charming small Christmas tree shapes onto your prepared parchment paper, leaving about an inch between each one. Immediately sprinkle them with tiny festive sprinkles for extra sparkle!
Bake the cookies for 1 hour. After baking, turn off the oven completely but leave the meringues inside for 2 more hours (or even overnight for the best crispness) to dry out fully and become perfectly delicate.
Once completely cool, gently lift the meringue trees from the parchment paper. Store them in an airtight container in a cool, dry spot. Just before serving, dust with a little powdered sugar for an elegant, magical finish!