12 ounces semisweet chocolate, coarsely chopped,
or 12 ounces semisweet chocolate chips
2/3 cup heavy cream
1 tablespoon unsalted butter (at room temperature)
1 tablespoon vanilla extract
1/2 cup unsweetened cocoa
Place chocolate in a medium mixing bowl. Set aside.
Warm cream in a small saucepan over low heat. As soon as you start to see bubbles around the edges of the pan, turn off the heat and pour the warm cream over the chopped chocolate. Stir until the chocolate melts and the mixture is completely smooth. Add the butter and stir until it is completely incorporated. Stir in the vanilla extract. Place the mixture in the refrigerator for 1 hour, or until it is firm enough to shape into balls.
Scoop out a heaping teaspoonful of the chocolate mixture and roll it into a ball between your palms. Roll the ball in cocoa until it is completely covered. Roll it lightly in your palms again to make sure the cocoa sticks, then re-roll the truffle in cocoa. Repeat with the remaining chocolate mixture. If the mixture gets too soft to hold its shape, place it back in the refrigerator for 10 minutes, until it can be handled easily.
Store the truffles in layers, separated by wax paper, in an airtight container in the refrigerator for up to 2 weeks. They are best served at room temperature.
Add 3 tablespoons almond liqueur (such as amaretto) with the butter. If desired, you may also roll the truffles in 1/2 cup finely chopped almonds instead of cocoa powder, or push a whole toasted almond inside the rounded truffle before rolling it in the cocoa.
Add 3 tablespoons whiskey with the butter.
Add 3 tablespoons orange liqueur (such as Grand Marnier) and 1 teaspoon finely grated orange rind with the butter.