Melt the butter in a double boiler over simmering water (medium heat).
Stir in the chocolate until melted.
Add a few spoonfuls of the warm chocolate mixture to the egg yolks in a separate bowl and mix until combined.
Stir the chocolate egg mixture back into the double boiler until combined.
Continue stirring until the temperature of the mixture is 160 degrees (about 4 minutes)
Remove the truffle batter from the stove and pour it into a bowl.
Allow the batter to cool for an hour, stirring occasionally.
Stir in 1/3 cup of Chambord.
Cover the truffle batter with plastic wrap and refrigerate for 8 hours or overnight.
Make 1-inch truffle balls.
Roll truffles in the cocoa powder.
If desired, pipe a frosting rose on top. See frosting instructions.
Store the truffles in refrigerator.