Mix the flour and milk until smooth.

Pour the flour/milk mixture into a small saucepan and cook over low heat until it’s thick and smooth. Prepare for this part to take awhile! Don’t rush it.

Stir frequently. There will be a point when you think the frosting is done and fully thickened. Keep stirring and cooking until it basically forms a loose ball in your saucepan.

Let this fully cool.

Cream the sugar and butter and vanilla in a mixer until smooth.

Add the cooled flour mixture.

Beat in the mixer until smooth. You want all the coarseness from the sugar to be gone, and the frosting to be kind of fluffy.

Put the frosting in the refrigerator for about 30 minutes before you frost your cooled cake.