On Food and Cooking

you’re starting with water as the continuous
phase. As the fat molecules are released into
the water, they’re surrounded by water — and
by the substances contained in the butter’s
own water droplets, which merge right into
the cooking water. The droplets contain milk
proteins and remnants of the emulsifier
membranes that coated the fat globules in the
original cream. And those protein and
phospholipid remnants reassemble themselves
onto the fat as it melts into the water, coating
and protecting separate fat droplets and
forming the fat-in-water emulsion. However,
the droplet coatings in this reconstituted
cream are sparser and more fragile than the
original fat-globule membranes, and will
begin to leak fat if heated close to 140ºF/60ºC.
Any water-based sauce can thus be
thickened and enriched simply by swirling a
pat of butter into it at the end. This is
especially handy in the last-minute thickening
of pan juices, which don’t have the benefit of