Balsamic-Port Reduction Sauce

=Balsamic-Port Reduction=
 * 4 cups vegetable stock
 * Stems from Shiitakes used below, halved lengthwise
 * 1/2 cup Balsamic vinegar
 * 1/2 cup Port wine
 * 1/2 tsp salt
 * 1 Bay leaf

Bring stock and mushroom stems to a boil, reduce heat and simmer for 15 minutes. Remove from heat and let steep for 30 minutes. Strain into another pot, add remaining ingredients and simmer until reduced to about 1/2 cup. Strain again.