4 tablespoons butter
½ cup onions (small dice)
½ cup water
8 ounces mushrooms
1 teaspoon salt
1 teaspoon sugar
1 tablespoon soy sauce
½ teaspoon tarragon
2 tablespoons cornstarch
1 tablespoon sherry

Melt butter; add onion and sauté till transparent. Add the remaining ingredients except the cornstarch and sherry. Bring mixture to a boil, then adjust to a simmer and reduce till almost dry. Dissolve cornstarch with sherry and add to the reduced mushroom mix. Cookout at a simmer till thickened and remove. Keep refrigerated until needed.