Line 11x15 jellyroll style pan or baking sheet with edges with aluminum foil. Melt chocolate bark according to package directions. Add peppermint extract and mix until well blended. Spread melted chocolate mixture evenly into pan reaching to all edges and corners.
Place baking sheet in freezer for 5 minutes. Do not leave in any longer or your second layer will not stick to the chocolate.
In the meantime, melt white chocolate bark according to package directions. Once the 5 minutes is up, take tray out of freezer and spread melted white chocolate over chocolate layer.
Immediately sprinkle crushed peppermint candies over white chocolate and pressing in candies if necessary.
Let bark harden at room temperature, about 30 minutes (or you can put it in the freezer again for a quick freeze). When harden, remove bark and foil from pan and break up bark into chunks. Store in an airtight container for up to two weeks or in freezer for up to three months.