Tip the chocolate and butter into a medium heatproof bowl and melt over a pan of barely simmering water, taking care not to allow the bottom of the bowl to touch the water. Once the chocolate mixture is melted and smooth, add the rum, cocoa powder and orange zest and mix. Remove from the heat and use a rubber spatula to fold in the biscotti, cherries, apricots, pistachios and almonds until thoroughly combined.
Transfer the mixture to a piece of parchment and roll into a log about 7 inches long and 2 inches in diameter; make sure the log is tightly rolled by twisting both ends of the parchment. Refrigerate for at least 2 hours to chill.
Spread the confectioners' sugar on a plate. Remove the paper from the log and roll it in the confectioners' sugar, brushing off any excess. Allow the log to sit at room temperature for about 15 minutes. Using a serrated knife, cut the log into 1/2-inch slices
Or, if you are aren't eating it immediately, store the log in the fridge. If you are gifting it, wrap it in parchment.