It is important to use a very high quality chocolate when making truffles. Callebaut and Valhrona chocolate are two good choices.

Center Mixture
8 ounces cream
1 pound bittersweet chocolate
1 ounce butter
1 ounce Cognac

Bring the cream to a boil; pour it over the cut chocolate. Allow to stand for 1 to 2 minutes, then stir until very smooth.

Beat in softened butter and cool to set.

Beat with an electric mixer, using the paddle attachment if available, on medium speed until light. Beat in Cognac. Pipe out small truffles on parchment or wax paper with a pastry bag fitted with a 1/2-inch plain tube. Refrigerate to set.

Enrobing
1 pound bittersweet chocolate
1 pound cocoa

Melt chocolate. Sift the cocoa into a deep pan. Dip the truffles into the melted chocolate and then set them in the cocoa, shaking the pan to cover them. After the covering sets, shake the truffles in a strainer to remove excess cocoa.