01 - Preheat oven to 250°F. Line two baking sheets with parchment paper.
02 - In a clean, dry mixing bowl, beat egg whites and cream of tartar with electric mixer on medium speed until foamy.
03 - Gradually add sugar, 1 tablespoon at a time, while beating on high speed. Continue beating until stiff, glossy peaks form (about 6–8 minutes).
04 - Beat in salt, vanilla, and peppermint extract until just combined.
05 - Gently fold chopped dark chocolate and mint chips with a spatula until evenly distributed.
06 - Using two spoons or piping bag, drop or pipe mounds of meringue (about 2 tablespoons each) onto prepared baking sheets, spacing 1 inch apart.
07 - Bake for 60 minutes, then turn off oven and let meringues cool inside undisturbed for 30 minutes to dry out.
08 - Remove from oven and let cool completely on baking sheets before serving or storing.