I have to thank Martha Stewart for this one, or, more likely, the unnamed but talented chef Martha Stewart paid for this recipe. It comes from Martha Stewart's Cookies.
3 egg whites
¾ cup sugar
½ teaspoon peppermint extract
Mix the whites and sugar in a metal bowl or the metal bowl of a stand mixer. Whisk the whites and sugar over but not in simmering water until the whites are warm and the sugar is completely dissolved. Beat the whites until soft peaks, add the peppermint extract, and continue beating until the whites form stiff, glossy peaks.
Fit a pastry bag with a star point, then paint one or two stripes on the interior of the bag with red food coloring gel or paste. Fill the bag with the meringue and pipe it onto a baking sheet lined with parchment paper. Put into a cool oven (175°F) until the meringues are dry. If you make small meringues, it may take as little as 30 minutes to dry them; large meringues can take 1½ hours.
6 ounces bittersweet or semi-sweet chocolate
1 cup cream
Melt the chocolate over but not in simmering water, then stir in the cream until thoroughly mixed. Let the ganache cool to room temperature.
To make the sandwiches, either use a small spatula or a pastry bag with a plain tip to spread ganache on the bottom of a meringue. Make a sandwich with a second meringue and rest it on a cooling rack until the ganache has set. Repeat until done.
These are rather time-consuming to make, so if you are in a hurry or simply don't have the patience, you could just dip the bottom into tempered chocolate and let them dry upside down. They won't be sandwiches but they'll taste just as good.