Preheat oven to 225°F (110°C) and line a baking sheet with parchment paper.
In a clean, dry mixing bowl, beat the egg whites and cream of tartar on high speed until soft peaks form.
Gradually add the sugar, one tablespoon at a time, beating until stiff peaks form and the mixture is glossy.
Gently fold in peppermint extract and a few drops of green food coloring, if using.
Transfer the meringue mixture to a piping bag fitted with a star tip and pipe small swirls onto the prepared baking sheet.
Bake for 90 minutes or until dry and crisp. Turn off the oven and let meringues cool inside with the door slightly open.
Melt the chocolate chips with vegetable oil, then drizzle over the cooled meringues.
Allow chocolate to set before serving. Store in an airtight container.