To make the centers: Place the chocolate in a heatproof bowl. Heat the cream to a simmer, and pour it over the chocolate. Let the mixture sit for 3 minutes, then stir until smooth. If the chocolate doesn't melt completely rewarm briefly in the microwave in 15-second intervals, stirring in between, until the mixture is smooth., Add the flavors or flavor combinations of your choice. Stir until everything is well-combined., Line a 9" x 13" baking sheet with parchment or plastic wrap, and pour the chocolate over it; don't spread it out. Cover the pan, and refrigerate for 60 to 90 minutes, until the mixture is thick and "scoopable.", To assemble the truffles: When the mixture is cool enough to hold its shape, scoop small balls of the chocolate onto a baking sheet that's been lightly dusted with cocoa. For perfectly round truffles, quickly roll each one between the palms of your hands. You have to do this quickly, or the chocolate will become too soft., Refrigerate the centers, rolled or just scooped, for about 30 minutes, covered, until they've firmed up a bit., To take the simplest route, coat the shaped centers in unsweetened cocoa powder (Dutch-process preferred, as it's smoother in flavor than natural)., Put the cocoa in a shallow pan and roll the centers around in it; or place cocoa and 4 or 5 centers at a time in a plastic bag, and shake gently to thoroughly coat., To coat with melted chocolate, heat 2 cups of the chopped chocolate (reserving some to add later) in the microwave until it's melted., Add the remaining chopped (unmelted) chocolate to the melted chocolate. Stir constantly until the chocolate is thick and shiny., If you have a chocolate dipping tool, use it to dip each center in the melted chocolate, setting the dipped truffles on a piece of parchment or on a plastic-lined wire rack., Immediately, as you make them, sprinkle each truffle with the garnish of your choice., Truffles will keep, well covered, for a day in a cool dry place, or refrigerated for up to 2 weeks.