Line 8x8x2-inch baking pan with foil, or 8x14-inch pan for doubled recipe
Bring cream to boil in heavy medium saucepan. Remove from heat. Add chocolate and whisk until melted and smooth. Blend liqueur and orange peel until peel is finely chopped and add to chocolate-cream mixture. Pour into prepared pan and freeze just until firm, 30-45 min.
Lift chocolate block out of pan onto work surface. Flatten foil at edges and cut into 25 squares. Shake pieces a few at a time in a container with cocoa powder and shake to coat, then transfer to a container with a lid and refrigerate or freeze until use. At room temperature these are too soft to handle easily.