1In a medium saucepan, combine the granulated sugar and milk.
Place the saucepan over medium heat and stir until the sugar is completely dissolved.
Remove the saucepan from the heat and let the mixture cool to room temperature.
In a large mixing bowl, beat the butter until it is light and fluffy.
Gradually add the cooled sugar mixture to the butter, beating continuously until the icing is smooth and creamy.
Use the buttercream icing immediately or store it in an airtight container in the refrigerator until ready to use.