Heat cream in a pot until it steams. Put chocolate in a bowl, pour hot cream on top, and stir until chocolate is melted and incorporated into cream.
Chill until solid all the way through, 1 to 2 hours. Using a chilled melon baller or latex gloves to prevent the ganache from melting or sticking to your hands, scoop out about a tablespoonful and quickly roll it into a ball. Repeat, lining truffles on a plate or a baking sheet.
If truffles become too soft to handle, place them in refrigerator or freezer for a few minutes. Roll them in cocoa powder, confectioners' sugar or a mixture of sugar and ground cinnamon. Serve immediately or store, wrapped in plastic, in refrigerator for up to 4 days.