Line a baking sheet with parchment paper. Set aside.
Place 2 chopped chocolate bars in the top pan of a double boiler over hot but not boiling water. (You may also use a glass or metal mixing bowl on top of a saucepan half filled with water.) Allow the chocolate to melt, stirring occasionally. Remove from heat and let stand to cool for 15 minutes.
Stir remaining 1 bar of chopped chocolate into the melted chocolate. Stir until melted and smooth.
Stir in 3/4 cup peppermint chunks. Pour mixture onto the prepared baking sheet. Spread about 1/4 inch thick. Sprinkle with the remaining peppermint chunks.
In a small microwave-safe bowl, microwave the white chocolate on medium power (50 percent) in 30 second intervals, stirring between intervals until melted.
Remove and stir. If chocolate is not melted, return it to the microwave and repeat the heating step, stirring every 30 seconds to avoid scorching.
Spoon white chocolate mixture into a large self-sealing plastic bag. Snip off one corner; drizzle chocolate over bark.
Chill for 30 minutes or until firm. Use parchment to lift candy; break into pieces. Store between sheets of waxed paper in an airtight container at room temperature up to 3 days or in the refrigerator up to 2 weeks.