In a medium saucepan over medium heat whisk together the sugar, flour, and salt. Cook for roughly 2 minutes to toast the flour.

Slowly add in the milk, whisking to combine. Whisk continuously until the mixture simmers and has thickened and is the consistency of thick pudding. Lay plastic wrap directly on the surface of the mixture and set aside to cool completely, roughly 2 hours. (This mixture can be made the day before and kept in the fridge.)

Next, add the butter to the bowl of a stand mixer and whisk on high until light and fluffy, roughly 2-3 minutes.

Slowly add in the cooled flour mixture one spoon at a time as you whip. Lastly, add in the vanilla and whip until the frosting is light and fluffy. Set aside until needed.

Decorate my Red Velvet Cake with this frosting.