[Suzanne]

For baked goods, the one way to (almost) ensure consistent results is to weigh ingredients instead of measuring by volume. There can be huge variations in the amount of flour in a cup depending on how "fluffed" it is before measuring, or how much it gets packed in the measuring cup, or how straight across the top of the cup it's wiped.

Another variable is the eggs: even eggs of the same "size" can differ. So again, if you use an identical weight of shelled eggs (already mixed together yolk and white), you're more likely to have the same results.