To prepare chocolate-peanut butter mixture and chill: Heat cream with peanut butter in a 1-quart heavy bottomed saucepan. Use a whisk to break up peanut butter so it melts evenly. Meanwhile, melt chocolate in the top of a double boiler over barely simmering water. When chocolate and peanut butter is smooth, combine with melted chocolate, using a whisk. Force through a medium-mesh sieve into another bowl, using a rubber spatula. Stir in vanilla. Let cool, then cover and chill 2 to 4 hours (or overnight).

To up to shape truffles: Whisk powdered sugar and cocoa together, then sift into another bowl to combine thoroughly. Grind peanuts, if using, in the bowl of a food processor fitted with the steel blade. Line a large baking sheet or tray with waxed paper or 30 to 50 1-inch paper candy cups (yield will depend on the size of your scoop used to shape truffle).

To shape truffles: If very chilled, let mixture sit out at room temperature for 20 minutes to soften slightly. Scoop out or spoon small portions of chilled filling and roll into a ball. If desired, push a "Goober" through the side, into center of round and roll to correct shape. Roll truffle in cocoa mixture or ground nuts and place in candy cups. Place in a decorative tin or gift box, separated by sheets of waxed paper or decorative foil. Keep chilled to maintain best flavor and texture.