Add vanilla and gradually add sugar, one cup at a time, beating well on medium speed.
Scrape sides and bottom of bowl often. When all sugar has been mixed in, icing will appear dry.
Add milk and beat at a medium speed until light and fluffy.
If you need to thin this icing, add a small amount of light corn syrup.
For best results, keep icing bowl in refrigerator when not in use. It can be refrigerated in an airtight container for up to 2 weeks. Rewhip before using. Yields 3 cups.
Notes
We recommend adding the powdered sugar slowly to the frosting because it keeps the frosting from crystallizing and doesn’t make it chunky. It just makes it smooth. It also allows you to see how much more powdered sugar you need.