Line a sheet tray with parchment paper and set aside.
Place ¾ of the chocolate in a large glass bowl and microwave on high power for 20 to 30 seconds. Stir with a rubber spatula. Continue to heat and stir in 30-second increments until the chocolate is just melted. Immediately add the remaining chocolate and allow to sit at room temperature, stirring often, until it’s completely smooth, slightly cooled, and glossy.
Stir in almonds and hazelnuts. Pour mixture onto prepared sheet tray and, using a small offset spatula, smooth into a rough rectangle, using the thickness of the nuts as a guide.
Refrigerate until firm, 30 minutes to 1 hour. Crack or cut bark into equal pieces and enjoy.