Combine the bittersweet chocolate, butter heavy cream in a heavy, small saucepan. Cook and stir over low heat until chocolate is melted, stirring constantly. Gradually stir about half of the hot mixture into the egg yolk, Return entire mixture to the saucepan. Cook and stir over medium heat for 2 minutes.
Remove the saucepan from the heat and stir in the champagne and orange zest. Transfer the truffle mixture to a medium mixing bowl and chill for 1 hour or until mixture is completely cool and smooth, stirring occasionally.
Beat the cooled truffle mixture with an electric mixer on medium speed for about 1 minute, or until the color lightens and mixture is slightly fluffy. Chill the mixture for 30 minutes more, or until it holds its shape. Using a small ice cream scoop or spoon, scoop 1 inch truffles, rolling them in your hand until smooth. Place balls on a baking sheet lined with waxed paper.
Roll the balls in cocoa powder, powdered sugar, almonds, and coconut flakes.
Melt the white chocolate in a microwave set on 50 percent power in 30 second intervals, stirring the white chocolate often, until melted. Dye with food coloring if desired, and drizzle over truffles. The chocolate will not stick to the truffles coated with cocoa powder and powdered sugar, so it is best to leave those bear. Refrigerate the truffles until firm and enjoy.