Melt bittersweet chocolate, unsweetened chocolate, whipping cream, and unsalted butter together in a heavy pan on low heat, stirring occasionally.

Pour the melted mixture into a small bowl and let it cool.

Refrigerate the mixture for 2 hours or until hardened.

Using a melon baller or teaspoon, quickly form the mixture into approximately 3/4-inch rounds.

Refrigerate the rounds until cold.

Roll the chilled truffles in cocoa or dip them in melted chocolate.

Refrigerate the truffles for up to 2 weeks.

For Orange Liqueur Truffles, add 1/4 cup of Grand Marnier, Cointreau, or Triple Sec to the melted truffle mixture, and stir in 1/4 tsp grated orange rind.

For Kahlua Truffles, add 3 tbsp of Kahlua to the melted truffle mixture.

For Rum Truffles, add 3 tbsp of rum to the melted truffle mixture.

For Dark Chocolate Coated Truffles, melt 8 oz bittersweet chocolate in a heavy pot over low heat.

Remove from heat and place cold truffle on a skewer or dipping fork.

Swirl the truffle in the melted chocolate to coat.

Place the coated truffle on wax or parchment paper to set.