Preheat your oven to 225 degrees F. Line a baking sheet with parchment paper. Set aside.
In the bowl of a stand mixer with the whisk attachment, beat the egg whites, cream of tartar, peppermint extract, and salt on medium speed unilt soft peaks form.
With the mixer still running, add the sugar, 1 tablespoon at a time, until stiff shiny peaks form. Set aside.
Place a large star tip into a piping bag. Use a popsicle stick (or squeeze directly from the gel bottle) and make 3 thick stripes up the sides of the bag, evenly spaced, being sure to put stripes in the piping tip as well.
Carefully spoon the meringue into the bag. Pipe 1-inch meringues onto the prepared baking sheet. (The first few will have really dark stripes. They'll lighten up as you go.)
Bake for 50 minutes. Then turn off the oven and leave the cookies inside for 4 hours (or overnight) without opening the door.