Prepare a piping bag, if using. Ensure that your piping tip has a hole big enough for the mini chocolate chips (they're bigger than you think). My piping tips really aren't conducive to this, so I just forgo the tip entirely and use the piping bag directly.
Add to a large bowl three egg whites, ⅛ tsp salt, ⅛ tsp cream of tartar, ⅛ tsp peppermint extract⅛, and green food coloring. (Exact amount of food coloring will depend on brand and what shade of green you prefer. Start small and you can always add more.)
Begin beating egg white mixture with a hand or stand mixer until the liquid egg whites froth and become opaque white, beginning to double in size.
While still continuing to whip, slowly add in the sugar. Make sure to scrape down the sides once all sugar is added, then resume whipping. It should turn glossy.
Whip until stiff peaks form. This means that if you remove a beater from the batter, it will retain a peaked shape pretty rigidly.
Add in chocolate chips; optionally you can reserve ¼ cup to sprinkle on top later if desired. Gently fold with a spatula, stirring as little as possible so as not to disturb the air whipped into the meringues.
Transfer to a piping bag, if using. Pipe meringue cookies onto a baking sheet 2" apart. Alternatively, grab a spoon and plop a heaping Tablespoon of meringue onto the cookie sheet. Sprinkle tops with reserved chocolate chips as needed.
Bake at 300°F for 10 minutes, then reduce oven temperature to 250°F and cook for an additional 10-15 minutes. You want the meringues to be dry, with just a bare hint of brown on the bottoms.
Once the meringues have baked 20-25 minutes, turn off the oven leaving the meringue inside. Allow to cool in the oven for 20-30 minutes before serving or storing. Store in an airtight container. Meringues may be a little chewy inside if underbaked (but I actually like them this way). They also may get a bit chewy after storing a few days if they absorb moisture in the air.