Mustard sauce—a popular sauce for fresh herrings, pork, &c.
—is made in this way :—Melt half an ounce of butter in a small
saucepan, blend with it half an ounce of flour, and a heaped-up
teaspoonful of French mustard with a pinch of salt ; when
thoroughly mixed, add half a pint of broth or water ; let it
come to the boil, then strain through the pointed strainer into
a hot sauce-boat. If Durham mustard is used mix it first with
a little tarragon vinegar.