Place the chocolate in a medium heatproof bowl and set aside.
In a small saucepan, bring the cream to a boil. Pour over the chocolate, let sit for 2 or 3 minutes, then whisk until smooth and shiny. Cool slightly. Whisk in the liqueur, if using.
One at a time, dip fruit, dried fruit, candied citrus peel, and crystallized ginger halfway into the warm ganache to cover by half. Place on a wire rack with parchment, wax paper, or foil underneath. Let stand until chocolate has dried.
To make truffles, let ganache cool completely in the refrigerator until hard. Scoop small balls of the hardened ganache and shape by hand. Roll truffles in the cocoa powder to coat. ;
Recipe courtesy of Wolfgang Puck, adapted from "Spago Chocolate," Random House, 1999