The Best Way to Split an Egg Is When You Cut a Recipe in Half
Some recipes are easy to cut in half or thirds; one cup of sugar becomes half, or half a teaspoon of baking powder becomes 1/4 teaspoon. And then there’s the egg, the only thing math can’t separate. If you have a cookie or cake recipe that you’re trying to cut in half or in thirds and it comes out with an odd egg, you need to grab a whisk.
The most reasonably accurate way to split one egg is to shake it up and pour it out. If you shake the egg well, the membranes will break so that the yolks and whites can evenly combine. You’ll get a more accurate ratio of egg representation, and with damaged membranes, you’ll be able to more accurately stop the flow when pouring. Pour out exactly what you need for your recipe, using a kitchen scale to weigh it out.
Depending on where the recipe was written, the recipes refer to the average size of eggs in that particular country. In the US this would be a large egg, but in the UK the recipe would refer to a medium egg (there is a helpful chart here). Assuming you’re in the US, large eggs weigh about 2-2.2 ounces each without the shell. Luckily, this number makes it fairly easy to split the recipe in half. If you get it wrong by half an ounce, your recipe will turn out just fine.
Try not to use one part of the egg as a “half”. It may be tempting to skip the whipping and use just the yolk or white, but egg yolks are heavier and, perhaps more importantly, each adds a different quality to your baked goods. Egg yolks add richness, density, and dryness, while egg whites can aerate, gel, and dry surfaces. Adding an extra half of the yolk to a cookie recipe can make the final product more powdery, and too much egg white can make the cookie flatter (and more shiny). Have I done this in a hurry before? Most definitely, and I lived to regret it. Once I really messed up a Finnish pulla bun. It was supposed to have sweet cheese in the center and suffice it to say it was a mess.
There are some recipes where this doesn’t matter, such as pancakes. It’s important, but it doesn’t matter . Sometimes you make pleasant discoveries this way. Perhaps 10 years from now, your family’s secret waffle recipe will use yet another egg white. But if you put in the effort to do something, you can do it right. Also keep in mind that the smaller the batch, the more important it will be to accurately measure the eggs.