Makes about 620g (or 3¼ cup) of buttercream, enough to generously frost about 12 cupcakes or a two-layered 20-cm (8-inch) cake.
Ingredients
35g (or 4½ tablespoons) all-purpose flour
200g (or 1 cup) granulated sugar
pinch of salt
240ml (or 1 cup) milk
226g (or 1 cup) unsalted butter, softened at room temperature*
½ teaspoon vanilla extract
Instructions
Combine flour, sugar and salt in a medium-sized saucepan. Whisk together. Add the milk and whisk until combined.
Place saucepan over low heat and allow the mixture to come to a boil, whisking continuously. Once the mixture starts bubbling, cook for 1-2 minutes, then take the pan off the heat and whisk for a minute to beat some of the heat out of the pudding.
Using a rubber spatula, scrape the pudding onto a clean plate and immediately cover it with plastic wrap, pressing the plastic wrap directly onto the pudding. This keeps a skin from forming. Allow the pudding to cool to room temperature.
Once the pudding has cooled, beat the butter in a medium-sized bowl until smooth and fluffy and lightened in color, 5-7 minutes.
Add the cooled pudding (which will look like glue at this point) one tablespoon at a time, mixing well after each addition. Once all the pudding has been added, mix for another few minutes, until the buttercream looks thick, smooth and creamy. Add the vanilla and mix briefly to combine.
Finally, use a rubber spatula to smush the buttercream against the sides of the bowl (aka: stir vigorously for about a minute) to get rid of any large air bubbles. This makes piping the buttercream a lot easier.
Use immediately or store, covered in the fridge, for up to seven days. Before you want to use it, allow buttercream to come to room temperature and mix briefly until smooth and creamy again.
Buttercream can also be frozen in a zip-lock bag for up to two months. Allow to thaw in the fridge overnight, then allow to come to room temperature and mix until smooth and fluffy before use.
Frosted cakes or cupcakes stay fresh, stored in an airtight container in the fridge, for up to three days. Allow to come to room temperature before serving.
Notes
* I usually take the butter out of the fridge 30 minutes before I want to start mixing.
Recipe by The Tough Cookie at https://thetoughcookie.com/2015/06/07/how-to-make-flour-buttercream-or-ermine-buttercream-the-battle-of-the-buttercreams-2-0/