When following Julia Child's recipes, you will often read something about "making the ribbon". If you prepare cakes the "old fashioned" way, that is, without using baking powder, it is an easy and essential step to make sure that your egg yolks and sugar mix fully before adding any additional ingredients.
In order to make the ribbon, you start with egg yolks and sugar. The sugar can be granulated or superfine, but the principle and steps are the same.
In a bowl, mix the egg yolks for a minute. They will get a bit of a sticky consistency and deepen in colour.
When you add the sugar, make sure it is done gradually in very small increments.
Start adding the sugar in a steady stream while beating. Slowly does it best since the sugar will incorporate better into the yolks. Keep beating at medium or med-high speed, or by hand, for about 3 minutes or until the mixture turns pale in colour and gains volume.
Look at the "ribbon" on upper right side of the photo.
You'll know when it's done when you lift your beater and let a stream of the mixture fall back. It will form what Julia Child calls a "slowly dissolving ribbon".
And there you have it. The beauty of using this method is that you ensure an even mix between the yolks and sugar before adding any other components. It also increases in volume, which is very helpful when making cakes with no baking powder as you will want to have as much volume as possible in your mixture when it goes into the oven.
Now go ahead and enjoy baking.