Creamy Lima Bean Gratin

• MAKE-AHEAD
• STAFF-FAVORITE

Ingredients

1. 4 tablespoons unsalted butter, 2 tablespoons melted
2. 2 large leeks, white and tender green parts, thinly sliced crosswise
3. 3/4 pound shiitake or cremini mushrooms, stems discarded and caps thinly sliced
4. 3 cups chicken stock or low-sodium broth
5. 3 cups heavy cream
6. 2 bay leaves
7. 1 tablespoon finely chopped tarragon
8. Salt and freshly ground pepper
9. Four 10-ounce boxes of frozen baby lima beans
10. 1/2 cup fine, dry bread crumbs
11. 1/4 cup freshly grated Parmesan cheese

1. Preheat the oven to 400°. In a large skillet, melt 2 tablespoons of the butter. Add the sliced leeks and cook over low heat, stirring, until they are softened, about 3 minutes. Add the mushrooms, cover and cook over low heat, stirring occasionally, until they are tender, 15 minutes. Add the stock, cream, bay leaves and tarragon and bring to a boil. Season with salt and pepper and remove from the heat.
2. Put the frozen lima beans in the bottom of a 12- to 14-cup glass or ceramic baking dish. Pour the hot cream mixture over the limas. Bake for 1 1/4 hours, or until the cream sauce is thickened.
3. Preheat the broiler. In a small bowl, toss the bread crumbs with the Parmesan and melted butter. Sprinkle the crumbs over the lima beans and broil for about 1 minute, rotating the dish for even browning. Let the gratin stand for 15 minutes before serving.