Combine sugar, peanut butter, butter, and vanilla in a bowl, mixing until very smooth. Chill 30 minutes. Roll candy into 48 balls, placing balls on waxed paper-lined baking sheet. Chill again.
Melt morsels and shortening in a double boiler. Poke a toothpick into the top of each ball, and dip ball into melted chocolate. Coat only the bottom half, leaving the top as is. Place back on waxed paper-lined baking sheet until chocolate is set, removing the pick after coating. Chill.
Wrap individually for storage in the refrigerator. Makes 48.
Not a NESTLÉ®-tested recipe.