Break up the dark chocolate into a heatproof bowl and add the butter.
In a small saucepan gently heat up the cream, the cracked cardamom pods, and the orange peel. Allow the cream to reach boiling point and then turn off the heat and allow the flavors to infuse for 30 minutes.
Reheat the cream until it is warm but not boiling, then strain the cream over the bowl containing the chocolate and stir everything until the chocolate has fully melted and the mixture is thick and glossy. Add the powdered sugar and a pinch of salt, mix again, and then allow the ganache to cool completely. Refrigerate the chocolate mixture for at least 4 hours.
When the chocolate has hardened, scoop up the ganache one tablespoon at a time, roll it into a rough ball shape, and then roll it in the cocoa powder. Store these orange cardamom chocolate truffles in the fridge, and take them out an hour before eating to enjoy them to their fullest.