Step #1 Place the butter In a large-ish mixing bowl.
Step #2 Add in 4 c sugar, then the milk & vanilla.
Step #3 On medium speed of an electric mixer, beat about 3-5 mins or until smooth & creamy.
Step #4 Gradually add the remaining sugar, 1 c at a time, beating well (about 2 mins) after each addition, until the icing is thick enough for good spreading consistency (you may not need all of the sugar).
Step #5 If desired, add a few drops of food coloring & mix thoroughly.
Step #6 Use & store the icing at about room temp because icing will set if chilled.
Step #7 The icing can be stored in an airtight container for up to 3 days.
Step #8 **If making a 3-layer cake, 3/4 c milk, use the following proportions: 1 1/2 c unsalted butter, 8-10 c confectioner's sugar, & 1 tbsp vanilla extract.