Preheat oven to 200 ℉ / 94℃
Line a baking sheet with parchment paper or a silicone mat.
Place egg whites, salt and cream of tartar in a large bowl.
Using the whip attachment, begin mixing on medium speed. Continue mixing until the egg whites become frothy.
Add peppermint extract to mixing bowl.
Increase mixer speed to medium high and begin adding sugar slowly (one tablespoon at a time).
Mix until stiff, glossy peaks form, about 3–5 minutes. The peaks should stand upright with slightly curled tips when the whisk is inverted. Note: Using a hand mixer may take longer.
Transfer ⅔ cup of meringue into a pastry bag fitted with a small star tip.
Divide the remaining meringue evenly, coloring half red and half green. Transfer the red meringue to a pastry bag fitted with a large round tip, and the green meringue to a pastry bag fitted with a large star tip.
To keep the parchment paper in place, add small dabs of meringue under the corners of the paper before placing it on the baking pan. This will help adhere the paper and prevent it from shifting during baking.
Pipe Christmas trees: begin by piping a star of green meringue approximately 1 ½ in diameter on parchment paper to anchor your tree. Then, pipe two more layers of stars, decreasing the size of each layer as you go.
Pipe Santa hats: begin by piping a red meringue base on parchment paper, about 1½ inches in diameter. Apply light, steady pressure as you raise the piping bag, creating a cone shape. Finish by stopping the flow of meringue once you reach the top of the hat, allowing the tip to taper to a point.
Pipe Santa hat 'fur': pipe mini stars around the base of the red Santa hats.
Bake in preheated oven for 1 ½ hours (note: the meringues should feel dry to the touch).
Turn off the oven. Leave meringues in the oven for an additional hour. This allows the meringues to continue to dry.
Remove meringues from the oven and place on a serving platter. Alternatively, place in an airtight container after cooled. Store for up to 5 days at room temperature.