In a medium mixing bowl, combine the graham cracker crumbs, sugar, and melted butter. Press the crumbs into the bottom and ½ way up the sides of a 9 or 10-inch springform pan. Place in the refrigerator to chill for 30 minutes.
In a large mixing bowl, beat together the cream cheese, powdered sugar, and vanilla with an electric mixer until smooth.
In a small microwave-safe bowl, melt the white chocolate chips in the microwave in 15-second intervals, stirring well between each heating interval until fully melted.
Pour the melted white chocolate into the cream cheese mixture and beat together with an electric mixer until smooth.
Fold in the thawed whipped topping.
Scoop the cheesecake mixture into the chilled graham cracker crust and use a spatula to smooth out evenly.
Refrigerate the cheesecake for 6 hours.
Preheat the oven to 200F degrees. Line two baking sheets with parchment paper; set aside.
In the bowl of a stand mixer, beat the egg whites, peppermint extract, and cream of tartar medium speed until the mixture is frothy and peaks begin to form.
While the mixer is running, add the sugar one tablespoon at a time, waiting a few seconds between each addition.
Add the green gel to reach your desired color.
Continue beating on medium-high speed until the mixture is very stiff and holds its shape.
Transfer the mixture to a piping bag with a large star tip.
Make the Christmas tree shape by piping in a circular motion with the base being about 1 inch across and make the circle smaller at you build the tree upwards to about 1 ½ inches tall. Be careful not to make them too large or the trees will fall over.
After piping all the trees, top each meringue with sprinkles if desired.
Bake the meringues in the preheated oven and bake for 60 minutes.
Turn off the oven and allow the meringues to sit in the oven for an additional 30 minutes.
Remove the pan from the oven and allow the meringues to cool completely to room temperature.
Run a butter knife around the edges of the springform pan to release the cheesecake, then open and remove the springform side.
Top the cheesecake with the meringue cookies right before serving.
Slice the cheesecake and serve chilled.