Step 1

In a small saucepan, whisk flour into milk together over medium-low heat, stirring constantly, until it thickens. It will be the consistency of a thick pasteMake sure that you whisk the flour and milk together well before you begin cooking it to avoid lumps.

Step 2

Remove from heat and let it cool to room temperature. This step is key. If your mixture is warm, it will melt your butter, and you'll end up with runny frosting.

Step 3

Stir in vanilla.

Step 4

While the mixture is cooling, cream the butter, sugar, and salt together until light and fluffy on medium high-high3, about 5 minutesMake sure that you scrape down the sides and really incorporate the butter and sugar to avoid gritty frosting.

Step 5

Then add the completely cooled milk mixture.

Step 6

Beat it for about 5 more minutes on medium-high to high until it looks like whipped cream. It may look separated at first, so keep beating it until it comes together and looks like a whipped cream.