Place chocolate in a microwave-safe dish. Microwave in 30-second increments until melted, about 2 minutes. Add peppermint extract and stir until mixture is smooth.
Line a baking sheet with parchment paper. Working with 1 cookie at a time, place a chocolate wafer into melted chocolate and turn to coat. With a fork, lift cookie from bowl, letting excess chocolate drip off. Transfer to prepared sheet. Refrigerate until chocolate hardens, about 10 minutes (or up to 1 week).