Creamy Mushroom Sauce

Originally this sauce was intended to be served over slices of polenta, but I recommend it on pork chops or medallions or even over pasta.

1 tablespoon extra-virgin olive oil
1/2 cup minced onion
1 pound mushrooms, such as white or cremini, sliced
2 cups stemmed and sliced shiitake mushrooms (4 1/2 ounces with stems)
1/4 teaspoon salt
1/4 teaspoon freshly ground pepper
1/2 cup white wine
1/2 cup reduced-fat sour cream
2/3 cup shredded fontina cheese (see Note)
2 teaspoons minced fresh tarragon

Heat oil in a large skillet over medium-high heat. Add onion and cook, stirring often, until lightly browned, 2 to 3 minutes. Stir in mushrooms, salt and pepper, and cook, stirring often, until the mushrooms are softened and most of the liquid has evaporated, 8 to 10 minutes. Pour in wine; bring to a boil and scrape up any browned bits from the bottom of the pan. Reduce the liquid until the pan is almost dry, 2 to 3 minutes. Stir in sour cream and bring to a simmer. Remove from the heat, stir in cheese and tarragon. Serve the sauce over the meat of your choice.

NOTE:
If you can’t find fontina, substitute another melting cheese, such as Gruyère or Swiss.