1. In a small saucepan, whisk together flour, milk, and salt. Bring to a boil over medium heat, whisking constantly. Continue cooking for 1-2 minutes, until mixture is very thick. If small lumps develop, whisk vigorously until smooth. Remove from heat and whisk in vanilla extract. Transfer to a small bowl. Press a piece of plastic wrap directly onto the mixture’s surface to prevent a skin from forming. Set aside to cool completely.

2. In the bowl of a stand mixer fitted with the paddle attachment, cream butter and sugar for about 5 minutes on medium-high speed, until very smooth, light, and fluffy. (Insufficient creaming of the butter/sugar will result in a gritty frosting.) Stop and scrape bottom and sides of bowl about halfway through.

3. Gradually beat cooled flour mixture into the creamed butter and sugar a few tablespoons at a time. Icing will begin to lighten. Gently scrape bowl and beat until mixture is fluffy and resembles whipped cream. (This takes about 3 minutes in my mixer, but time will vary based on your unit’s power and the temperature of your ingredients. I’ve heard it taking anywhere from 1-8 minutes. Keep an eye on it.) The mixture might look curdled when the flour paste is first added; additional whipping will smooth it out. Pipe or frost as desired.

Notes: Ermine Icing is susceptible to temperature fluctuations and will break down above 70 degrees F. It’s best when freshly-whipped. Cakes and cupcakes should be completely cooled before frosting.