The perfect finish to peanut butter cake, this also is delicious spread on chocolate, banana or other nut cakes!
In large bowl, beat peanut butter and butter with electric mixer until light and fluffy. Add vanilla, beat well. Gradually add sugar, one cup at a time, beating well on medium speed, and scraping sides and bottom of bowl often. When all sugar has been mixed in, icing will appear dry. Add milk and beat at medium speed until light and fluffy. Keep icing covered with a damp cloth until ready to use. For best results, keep icing bowl in refrigerator when not in use. Refrigerate in an airtight container. Re-whip before using.
Makes about 3 cups icing.