1-First Step: Prepare the milk flour base (mise en place) Whisk together 1/4 cup flour and 1/4 cup of the milk in a saucepan to form a smooth slurry. This prevents lumps in your boiled milk frosting. Gradually stir in the remaining 3/4 cup milk and 1 cup sugar. Place over medium heat. Cook, stirring constantly with a whisk, until the mixture thickens to a pudding consistency, about 8-10 minutes. It should reach 200°F if using a thermometer. Remove from heat, transfer to a bowl, and cover with plastic wrap pressed directly on the surface to avoid a skin. Chill in the fridge for at least 1 hour or until fully cooled. For vegan adaptations, use plant milk here.

2-Second Step: Soften and beat the butter While the base chills, cut 2 cups unsalted butter into tablespoon-sized pieces. Let it soften at room temperature until pliable but cool, about 65°F. In a stand mixer with paddle attachment or using a hand mixer, beat the butter on medium speed for 2-3 minutes until creamy and pale. This step builds structure for your flour buttercream. Add the pinch of salt and 1/2 teaspoon vanilla extract, beating another minute. Scrape down the bowl as needed. For low-calorie versions, incorporate the butter gradually to maintain lightness.

3-Third Step: Combine cooled base with butter Once the milk mixture is cold, add it to the whipped butter one tablespoon at a time. Beat on medium-low speed after each addition until fully incorporated. This gradual method ensures a silky Ermine icing for cakes without separation. Continue until all base is added, then increase to medium-high speed. Beat for 5-7 minutes until light, fluffy, and spreadable. The volume will double. Taste and adjust with remaining vanilla if desired. Gluten-free flour works seamlessly here with no texture change.

4-Fourth Step: Add final flavorings and whip Beat in the last teaspoon of vanilla extract. Whip on high for 1-2 more minutes for peak fluffiness. Your authentic Ermine frosting is ready! It should hold peaks but spread easily. If it seems too soft, chill 10 minutes before use. For variations, mix in extracts like almond during this stage. This cooked flour frosting pipes beautifully on carrot cake cupcakes.

5-Final Step: Frost and serve Apply immediately to cooled cakes or chill covered up to 2 days. Use an offset spatula for smooth finishes or a piping bag for designs. This vintage buttercream sets firm yet tender, ideal for layer cakes. Store any extras as noted below.