When making a cake from scratch I have always added my eggs one at a time, mixing in between each, because this is how I learned from my mother. I just can't remember why this is supposed to be beneficial. Does anyone know why this should produce a different result than adding them all at the same time?
The key thing here is a substance called
Doing the adding of the egg one-by-one, plus a few other things are...
So to recap, liquid and fat do not mix together. The egg has Lecithin that acts like a bond that keeps those 2 together. By flooding the mixture with the substance that will act like a binder (egg), you actually make it harder for all the water in the butter / eggs to bind to the fat in the butter / eggs.
Picture of Emulsion
Take note that in this picture, the oil to make the mayonnaise was added too fast in the failed picture. Take a look at thesproatingseed.com link below for even more information on emulsion!