About this recipe:This is a rich buttercream icing made with the addition of custard. It can be embellished by adding various flavoured liquors, aromatic essences and food colouring. This is my basic time-tested recipe for decorating cakes and cupcakes. Makes enough buttercream for one 3 to 4 layer cake or 24 cupcakes.
In a small, heavy saucepan beat egg with a fork, then mix in sugar and milk. Cook on medium low heat, whisking constantly, so that it does not stick to the bottom. When just starting to boil, start stirring non-stop until it thickens to a thin custard consistency. Take off heat and cool completely (see footnote).
Beat butter until light and creamy, around 5 minutes. Start adding cooled custard, 1 to 2 tablespoons at a time, beating after each addition. Add vanilla and any other flavourings at the end. Beat until a very light and fluffy consistency is reached.
Use the buttercream to decorate your cooled cake or cupcakes, ensuring they are cooled completely to prevent the buttercream from melting. For best results when using a pastry bag, chill the buttercream in bag in the fridge for 1 hour. Chilled buttercream creates better defined shapes when used for cake decorating.
It is important that custard is completely cooled, otherwise it will melt the butter. The custard can be made ahead and chilled in the fridge till needed.
This recipe contains quite a bit of butter, for ease of decorating with a pastry bag and to help the piped icing to hold its shape. If you don't intend to create elaborate decorations and just want to simply ice your cake, you can decrease the butter to 200g.
For chocolate version add 1 Tablespoon cocoa-powder or Nutella. You can omit vanilla, but I really like to add 1 Tablespoon of rum or cognac to this buttercream. Other liquors can create interesting variations too: coconut (Malibu), orange (Grand Marnier), lemon (Limoncello) - depending on the cake you have in mind.