Using an electric mixer or a whisk, beat the peanut butter and confectioners' sugar together until smooth and stiff. Beat in the vanilla extract. Shape the peanut butter mixture into 20 (1-inch) balls and place on a waxed paper-lined sheet tray. Place the tray in the freezer for 1 hour.
Add chopped chocolate to a small bowl set over gently simmering water. Stir to melt. Remove chocolate from heat. With 2 forks, carefully dip the chilled peanut butter balls 1/2 way into the chocolate, let excess drip off, and lay onto the waxed paper-lined sheet tray.
With a fork, swirl some decorative chocolate across the top of each bite. Place in the refrigerator for the chocolate to set and the peanut butter to solidify, about 30 minutes.
If it's a hot and humid day outside dust your hands with confectioners' sugar before rolling the balls. This will make it less sticky.