In a small pot, bring cream and peppercorns to a boil. Remove from heat, cover the pot and let the mixture stand for 10 minutes, to allow the flavours to infuse.
Strain the cream into a bowl and discard ⅔ of the peppercorns.
Pour the cream back into the pot, with the remaining ⅓ peppercorns and bring to a boil again. Put the bowl of chocolate nearby. As soon as the cream comes to a boil, strain it into the bowl of chocolate and stir until all the chocolate has melted.
Add unsalted butter, one piece at a time, stirring to fully incorporate until adding another piece. Let the chocolate cool for 1 hour. Cover and refrigerate for at least another 3 hours.
Place cocoa powder in a shallow dish. Using a spoon, shape the ganache into small balls and roll in the cocoa powder to coat. Set the truffles on a platter and serve.
