Heat milk and sugar in a heavy saucepan over medium-low heat with the vanilla
bean, which has been split lengthwise, scraped with the back edge of a knife and
added to the milk - seeds, pod and all. When the sugar is dissolved, raise the heat
to medium-high and hold between a simmer and a boil, stirring occasionally, for
about 1 hour. Be sure the milk doesn't stick to the bottom of the pan. The milk
will thicken, turn beige, and darken to light tan.
Strain into a bowl and cool. The milk will have reduced to 4 1/2 cups.
keep several weeks, covered, in the refrigerator.