1. Line a 15 x 11 x 1-inch jelly roll pan with nonstick aluminum foil.
2. Melt chocolate in a large bowl set over a saucepan of gently simmering water. Stir chocolate until smooth. Remove bowl and allow to cool 3 minutes.
3. Stir in mint extract and spread chocolate evenly onto prepared pan. Scatter candy cane pieces over top. Refrigerate for 2 hours.
4. Invert pan onto a cutting board and peel off foil. Break bark into thirty-six 2-inch pieces.
5. Store in an airtight container at room temperature for up to 2 weeks.