Step 1

Add the milk and flour to a medium sauce pan over medium heat and whisk well. Keep whisking over medium to high heat, until the mixture begins to thicken to the consistency of a gravy or pudding. Remove the saucepan from heat and allow the mixture to cool.

Step 2

While the flour and milk mixture is cooking, beat together the butter and sugar in a large bowl with an electric mixer. Beat well, at least 5 minutes. Make sure sugar and butter is well combined or your frosting will be a bit grainy. Beat in the vanilla until combined.

Step 3

Add the cooled flour mixture to the bowl and beat together until light and fluffy.

Step 4

Use frosting immediately or, if you prefer a stiffer frosting, refrigerate for 30 minutes before use.