This silky, smooth, creamy frosting will win your heart. Ermine Buttercream was the original frosting for Red Velvet Cake.
Place sugar, flour, and salt in a small saucepan and whisk together. Stir in milk. Cook over medium heat, stirring constantly until mixture comes to a boil. Continue to cook a very short time, stirring, until very thick.
Remove from heat and pour into a medium mixing bowl. Cool to room temperature.
When cool, whisk in a stand mixer, using whisk attachment or beaters if using a hand-held. Add butter a tablespoon at a time until smooth. Add vanilla and beat in. Chill frosting for a few minutes before decorating.
It is recommended to refrigerate cake or cupcakes until ready to serve; bring out in enough time to reach room temperature.