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 orange zest.
Pour mixture onto the prepared baking sheet. Spread about 1/4 inch thick. Sprinkle with pistachios and orange peel strips.
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.
