3 large egg whites, at room temperature
1/8 tsp cream of tartar
1/8 tsp salt
3/4 cup sugar
1/4 tsp vanilla extract OR 1/8 tsp peppermint flavouring
6-8 drops green food colouring (optional)
3/4 cup mini chocolate chips, semi-sweet
Set two racks in the center of the oven and preheat the oven to 250°F. Line two baking sheets with parchment paper.
In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites, cream of tartar and salt on medium-high speed (or high speed if using a hand mixer) until the egg whites are frothy, white, and hold a soft peak when the whisk is lifted out of the bowl, about 45 seconds. Continue to beat on medium-high speed, adding the sugar very gradually, taking about 2 minutes to add it all. Beat for 4 to 5 minutes more, until the meringue is glossy and stiff, with a shaving cream-like consistency. Beat in the vanilla (or peppermint) extract. Set 3 tablespoons of the chocolate chips aside. Add the remaining chocolate chips to the meringue and fold with a rubber spatula to combine.
Use two soup spoons to drop 1.5-in mounds of meringue onto the prepared baking sheets about 2 inches apart. Dot the meringues with the reserved chocolate chips, pressing them into the meringue just slightly. Place the meringues in the oven and bake for 30 minutes. Turn the oven off and let the meringues cool in the oven for 30 minutes more. Let the meringues finish cooling on the baking sheets on the countertop for about 1 hour, or until the chocolate chips are no longer soft. The cookies are best enjoyed fresh on the day they are made but leftovers can be stored in an airtight container for several days. Take care when stacking the cookies; they are fragile.