On Food and Cooking

collect at the surface. If a large volume of oil
is added before the previous one has been
fully emulsified, then the bowl may end up
with more unemulsified oil than water. The
oil then becomes the continuous phase, the
normally continuous water becomes dispersed
in it, and the result is an inside-out emulsion,
oily and runny. By whisking in the first
portion of oil in small doses, the cook makes
sure to produce and maintain a growing
population of small droplets. Then when the
rest of the oil is incorporated more rapidly
into the already well-emulsified system, the
existing droplets work as a kind of mill,
automatically breaking down the incoming oil
into particles of their own size. In the last
stages of sauce making the cook’s whisk need
not break up the oil drops directly, but has the
easier job of mixing the new oil with the
sauce, distributing it evenly to all parts of the
droplet “mill.”