Line 2 cookie sheets with waxed paper. Beat peanut butter, butter, and vanilla in a medium size bowl with electric mixer until smooth. Gradually beat in sugar and flour until well blended. Roll rounded teaspoonfuls into 1-inch balls. Arrange on prepared cookie sheets and refrigerate 1 hour or until firm. Spear one ball at a time with a wooken pick and dip in chocolate to cover about 2/3. Arrange chocolate side down on prepared cookie sheets. Smooth over tooth pick holes. Refrigerate about 15 minutes until chocolate is set. Store tightly covered in refrigerator up to 2 months (like they last that long