Heat the oven to 225°F. Line two large baking sheets with parchment so the meringues release cleanly.

In a small bowl, stir together the sugar and cream of tartar. This helps the sugar dissolve evenly later.

Add egg whites, vanilla, green food coloring, and salt to the mixer bowl. Beat on medium-low until the mixture looks foamy and even, about 1 minute.

Increase to medium-high. Sprinkle in the sugar mixture a spoonful at a time. Keep whisking until the meringue is glossy and forms stiff peaks that stand tall when you lift the whisk, about 2 to 3 minutes.

Fill a piping bag fitted with a star tip. On the parchment, pipe a large star as the base, then stack smaller stars on top to shape a tree. Add a sugar star and sprinkles. This is a fun job for little helpers.

Bake for 1 hour, rotating the sheets halfway through so they dry evenly. You want them set and matte, not browned.

Turn off the oven and leave the trays inside for at least 1 hour. This gentle cool-down keeps the shells crisp and helps prevent cracks.

Transfer to a wire rack to cool completely. Store airtight once cooled to keep that light crunch.