If the recipe calls for eggs, milk, or water, and oil, I first put the egg and oil together and beat it to form a smooth emulsion, as egg yolk is a natural emulsifier. I then beat in the liquid, which when all is done, forms a homogenized mixture. If I half to halve a recipe, I simply use half of the egg/oil/milk emulsion and store the rest in the fridge. I do this frequently with pancakes as I'm diabetic and can't eat them very often. But my wife loves them and I make them for her every Saturday. She can't eat a whole recipe's worth of pancakes, so I cut it in half. I get two batches of pancakes out of the egg/oil/milk mixture this way. The egg/oil/milk mixture can be frozen if need be.
Tip: Though it never says to do it in a recipe, I always combine the fat and egg first, to make that emulsion. I then beat it into whatever recipe I'm making; and I don't have to beat it as long before it blends into the other ingredients.
Seeeeeeya; Goodweed of the North