To melt the chocolate, chop it into uniform pieces and melt in the microwave or in a heavy bottomed pan or double boiler.
Line an 8 or 9 inch square baking pan with plastic wrap; set aside. (Alternatively, you can pour directly into a pyrex pan and scoop the truffles out, but this allows you to lift the entire block of truffles out of the pan.)
Place melted chocolate in a medium-size bowl. In a 1-quart saucepan, scald cream. To scald the cream, you heat it just until a skin forms on the top – do not boil. It looks as though a piece of plastic wrap has been stretched over the surface. Remove from heat and let cool five minutes. Stir vanilla into cream.
Beat the melted chocolate with an electric mixer. Stop mixer and pour in cream all at once over chocolate. Continue beating, cleaning sides and bottom of bowl several times with rubber scraper, until mixture is smooth and well-blended. This takes no more than 1 to 2 minutes.
Pour into prepared pan and refrigerate 8 hours or until firm.
Cut into 1-inch squares by lifting the block of truffles out of the pan and slicing them on a cutting board. Alternatively, you can cut them in squares to portion, and then form the portions into balls and coat with your choice of chopped nuts, cocoa powder or coconut.
Serve immediately or store in refrigerator for up to one week. These are very soft and delicate, and will melt in warm conditions, so they are best removed from the refrigerator right before serving. Makes 64 pieces.