The Food Lab: Better Home Cooking Through Science

So, remembering that foods cook from the outside in and
that the hotter your cooking environment, the greater the
temperature gradient that forms in your egg, you realize that
for soft-boiled eggs, you want to start with cold eggs and
submerge them in hot water, so that the whites cook and set
while the yolks remain liquidy. I tried plunging the eggs
directly into boiling water to cook until the whites were just
set, but I ran into a problem: the outermost layers of the
whites end up slightly overcooking. A much better way to
do it is to bring a pot of water to a boil, shut off the heat,
drop the eggs into it, cover the pot to help it retain some
heat, and then start the timer. Since the water in the pot gets
cooler as it sits, the eggs stand much less of a chance of
overcooking and turning rubbery.
The other important thing to consider is the ratio of water
to eggs—add too many eggs, and they’ll cool the water
down so much that they won’t cook properly. So, 3 quarts is
enough water to cook up to 6 eggs. Any more than that, and
you’ll want to cook in batches, or in a larger pot.