Add the powdered sugar one tablespoon at a time, with mixer running on low, until everything is incorporated and smooth. (eastofkitchen.com)
With the mixer on low speed, add powdered sugar one cup at a time, beating until combined after each addition and scraping down the sides as necessary. (flourcoveredapron.com)
Add powdered sugar one cup at a time, until mixture is thick enough to roll into balls that will hold their shape. (gourmetmomonthego.com)