2. To temper chocolate: Using a microwave, place 3/4 of chocolate in a microwave-safe glass or ceramic bowl (set aside remaining chocolate). Program microwave at 50 percent power. With bowl uncovered, heat chocolate for 30 seconds and then stir with a rubber spatula. Repeat, heating for 30 seconds and then stirring, until almost all the chocolate in the bowl is melted, about 4 minutes total.
3.Using an instant-read thermometer, check temperature of chocolate. It should be no more than 115°. If it hasn’t reached desired temperature, continue to heat (in 10-second increments). Then add reserved chocolate and stir constantly until completely melted and smooth and thermometer reads 88° to 90°. Chocolate is now tempered.
4. Stir nut mixture into bowl containing chocolate.
5.Using an offset spatula, spread chocolate in an even layer, about 1/4 inch thick, on the parchment. Sprinkle with reserved 1/2 cup nut mixture. Allow bark to cool until hard, at least 20 minutes. Break into irregular pieces.
Tip: Wrap in gift boxes or airtight tins lined with decorative waxed paper, or place in cellophane bags and tie with ribbon. Chocolate bark will last several weeks.