2 cups defatted turkey juices from turkey roasting pan or homemade turkey or chicken stock
1/2 cup heavy cream
3 tablespoons unsalted butter
10 ounces shiitake mushrooms, rinsed, stemmed and sliced
1 tablespoon chopped fresh thyme leaves
1 clove garlic, minced
1/4 cup dry sherry
Salt and freshly ground black pepper
1/2 teaspoon red wine vinegar
Bring the juice to a simmer in a small saucepan over medium-high heat and reduce by half. Add the cream and cook until reduced enough to coat the back of a spoon, about 8 minutes.
Heat the butter in a skillet over medium-high heat. Add the mushrooms, thyme, garlic, and sherry and cook, stirring occasionally, until tender and almost dry, about 6 minutes
Combine the mushrooms with reduced gravy and season with salt and pepper. Reheat, if necessary, and stir in the vinegar. Transfer to a gravy boat and keep warm until serving.