4 large egg whites, at room temperature
1 teaspoon cream of tartar
1/4 teaspoon fine sea salt
1-1/2 cups granulated sugar
1 teaspoon vanilla extract
1/4 teaspoon pure peppermint extract
green food coloring
6 ounces bittersweet chocolate (60% to 70% cacao), finely chopped
Position racks in the upper and lower thirds of the oven and preheat it to 350F. Line two baking sheets with parchment paper.
In the bowl of an electric mixer fitted with the whisk attachment, combine the egg whites, cream of tartar, and salt. Beat on medium-high speed until the whites reach soft peaks, about 2 minutes. With the mixer running, slowly add the sugar, 1 tablespoon at a time. When the sugar has been added, beat until the meringue reaches stiff peaks. Beat in the vanilla, peppermint extract, and a few drops of green food coloring to reach a soft, mint green color, like mint chocolate chip ice cream. Remove the bowl from the mixer and fold in the chopped chocolate.
Using 2 spoons, shape the meringue into small mounds, about 1-1/2 tablespoons each. Space the cookies about 1-1/2 inches apart on the prepared baking sheets (they won’t spread much).
When all the batter has been portioned, turn off the oven. Place the baking sheets in the turned-off oven and close the door. Allow the meringues to dry for at least 4 hours, but overnight is even better. Do not open the oven door at any point during drying. When the meringues are firm to the touch remove the pans from the oven. Allow the baking sheets to sit at room temperature to let the chocolate bits firm up before storing.
The meringues will keep in an airtight container in a cool, dry place for up to 3 weeks.