1 1/2 pounds green beans, trimmed and cut into 1 1/2-inch lengths
5 tablespoons (1/2 stick plus one tablespoon) unsalted butter
12 ounces cremini (baby portobello) mushrooms, thinly sliced
3 tablespoons chopped shallots
1/4 cup all-purpose flour
1 1/3 cups half-and-half
1 1/3 cups homemade chicken stock or canned reduced-sodium chicken broth
1 1/2 teaspoons soy sauce
salt and freshly ground pepper to taste
1/3 cup freshly grated parmesan cheese
Cook the green beans in a large pot of lightly salted water until crisp-tender, about 4 minutes. Do not overcook, because they will bake in the oven. Drain, rinse under cold water and drain again. Pat the green beans dry with paper towels.
Heat 4 tablespoons of the butter in a large saucepan over medium-high heat. Add the mushrooms and cook, stirring occasionally, until the mushrooms are tender and the liquid has almost evaporated, about 12 minutes. Add the shallots and cook, stirring often, until softened, about 1 minute. Sprinkle with the flour and stir well.
Whisk in the half-and-half, chicken stock and soy sauce, and bring to a simmer. Reduce the heat to medium-low. Simmer until slightly reduced, about 5 minutes. Add the green beans and mix well.
Spread in a buttered 2-quart baking dish. (The gratin can be prepared up to this point 1 day ahead. Press plastic wrap directly on the surface of the sauce, pierce a few holes in the wrap to allow the steam to escape, then cool to tepid and refrigerate. Remove the wrap before reheating.)
Position a rack in the center of the oven and preheat to 350 degrees.
Sprinkle the parmesan over the gratin. Cut the remaining 1 tablespoon butter into tiny cubes and dot the top of the gratin with butter. Bake until the sauce is bubbling and the top is browned, 25 to 35 minutes. Serve hot.
Can be made one day ahead.
>From "Thanksgiving 101"
Per serving (based on 10 servings): 145 calories, 5 grams protein, 10 grams fat, 6 grams saturated fat, 10 grams carbohydrate, 2 grams fiber, 29 milligrams cholesterol, 199 milligrams sodium