1. Combine chocolate, butter, and the 3 tablespoons whipping cream in a heavy 2-quart saucepan. Cook over low heat, stirring constantly, until chocolate is melted (about 10 minutes). Remove saucepan from heat.
2. Gradually stir about half of the hot mixture into the beaten egg yolk. Return egg mixture to saucepan. Cook over medium heat, stirring constantly, about 2 minutes or until slightly thickened. Remove saucepan from heat.
3. Stir in rum, brandy, or whipping cream. Transfer chocolate mixture to a small mixing bowl. Chill about 1 hour or until mixture is room temperature and smooth, stirring occasionally.
4. Beat the cooled chocolate mixture with an electric mixer on medium speed about 2 minutes or until slightly fluffy. Chill about 15 minutes or until mixture holds its shape. Drop mixture from a rounded teaspoon onto a baking sheet lined with waxed paper. Chill about 30 minutes more or until firm. Shape into smooth balls with hands, working quickly so the truffles don't get too soft.
5. Bring water to boiling in the bottom of a double boiler or a saucepan. Remove from heat. Place chopped chocolate-flavored candy coating in top of double boiler or in a heatproof bowl and set over the boiling water, making sure the bottom of the top pan is not touching the water. Stir frequently until coating melts. Or, melt coating in the microwave oven: In a 2 1/2-quart microwave-safe bowl, microwave candy coating on 100% power (high) for 2 minutes. Stir. If necessary, microwave 30 seconds more or until almost melted. Coating may not look melted until stirred.
6. Drop truffles, one at a time, into melted candy coating; turn truffles with a large, long-tine fork to coat. Lift truffle out with the fork without piercing the centers; draw fork across rim of pan to remove excess coating. Invert truffles onto a waxed-paper-lined baking sheet. If desired, twist fork slightly as candy falls to make a swirl on top.
7. Let dipped truffles dry until candy coating hardens. If the candy coating becomes too thick while dipping, reheat it in the microwave. Or, for coating that's been melted in a double boiler, replace the cooled water with warm water. Stir coating constantly until it once again reaches dipping consistency.
8. To decorate truffles, if desired, place melted vanilla-flavored or pink candy coating in a small, self-sealing plastic bag with a corner snipped off (opening should be very small) or a pastry bag fitted with a small, round tip. Pipe coating in a design atop truffles. Or, drizzle coating over truffles with a spoon. Let dry. Or, if desired, after chilling the shaped truffles for 30 minutes, roll them in finely chopped nuts instead of dipping them into melted chocolate. Makes about 30.