To avoid wasting the egg yolks, use liquid egg whites. An egg white weighs 30 g and measures 2 tbsp (30 ml). Therefore, you will need ½ cup (120 g) egg whites for this recipe.
If you have three 6-inch (15 cm) cake pans on hand, you can bake the three cakes at the same time.
The mixture may separate after you add about half of the butter. Everything should come together once you add the remaining butter. This step takes time, so don’t add the butter too quickly. If the icing seems too soft when you are ready to apply it to your cake, refrigerate it for a few minutes, then whisk it up again.
The icing can be prepared in advance if left covered at room temperature. Mix it well before applying it to your cake.
