Preheat the oven to 100°C/210°F. Line two baking sheets with parchment paper or silicone baking mats. Ensure your equipment is clean and free of grease to prevent issues with the meringue.

Place the egg whites in a large, clean mixing bowl. Using a handheld mixer or a stand mixer fitted with the whisk attachment, beat the egg whites on medium speed until they form soft peaks, approximately 3–4 minutes.

Gradually add half of the caster sugar, cream of tartar, and vanilla or peppermint extract while whisking. Continue whisking until fully combined.

Add the remaining sugar in small increments and continue to whisk on medium-high speed until the mixture forms stiff, glossy peaks. This process may take an additional 6–8 minutes. To test, rub a small amount of the mixture between your fingers; it should feel smooth, not grainy. If it remains grainy, whisk for another minute.

Incorporate a few drops of green food coloring gel and gently fold it into the meringue mixture until evenly distributed. Be cautious not to overmix, as it may deflate the batter.

Transfer the mixture to a piping bag fitted with a 1cm star nozzle. Pipe swirls onto the prepared baking sheets to form tree shapes, leaving 2–4 cm of space between each.

Sprinkle the meringue trees with red, green, and white sprinkles, mimicking ornaments on a Christmas tree.

Place the baking sheets in the preheated oven and bake for 1 hour. After baking, turn off the oven but leave the meringues inside to cool completely. This gradual cooling process helps prevent cracks. For best results, allow the meringues to cool overnight in the oven.

Once fully cooled, carefully peel the meringues off the parchment paper or mats. Serve immediately or store for later use.