Place egg whites in a large mixing bowl, and allow to stand at room temperature for 30 minutes.

Preheat oven to 225 degrees F. Line a baking sheet with parchment paper; set aside.

Add cream of tartar and salt to the egg whites, and beat on high until soft peaks form. The egg whites should curl over when you hold up the end of your beater. With the mixer on high, add sugar 1 tablespoon at a time to the egg whites. Continue to beat on high until stiff peaks form (the egg whites stand up straight when you hold up the beater). Beat in peppermint extract and green food coloring.

Transfer the meringue mixture to a pastry bag fitted with a large open-star tip. Pipe meringues 1" apart on the parchment paper. {I did swirls, but you could also hold the tip in one spot and let the meringue sort of squish out from the center.} Bake for 60 minutes, or until the meringues appear dry and are firm when touched. Turn off the oven, and leave the meringues in the oven for another 60 minutes until they crisp up and cool down.

In a small saucepan over low heat, melt together chocolate and oil; stir to combine. Spread 1/2 to 1 teaspoon chocolate onto the flat side of a meringue. Top chocolate with the flat side of another meringue, making a sandwich; press gently to seal. Repeat with remaining meringues. Let stand until set. {I put mine in the fridge for a few minutes to help speed things up.}