Reprinted with permission from Crazy for Casseroles by James Villas. Published by Harvard Common Press, Boston, MA.  New York, NY. Copyright 2003. All rights reserved.

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Potato, Wild Mushroom, and Sorrel Gratin

Baked slowly at a relatively low temperature, this is without question one of the most luscious vegetable casseroles in my entire repertoire. The flavor contrast of the mild potatoes, earthy mushrooms, and slightly bitter sorrel is phenomenal, and if you have plenty of time, bake the casserole at 300°F for up to 2 hours for even greater succulence, adding a little more milk or half-and-half if necessary to keep the ingredients moist. Fresh sorrel (which is also wonderful added to salads) is now available almost year round in finer markets, but do remember that the larger leaves can be tough and very bitter. If you can’t find sorrel, you might substitute either radicchio or arugula with different results.

2 tablespoons butter
1/2 pound fresh wild mushrooms (chanterelles, ceps, or shiitakes), stems removed or trimmed and thinly sliced
1 garlic clove, minced
5 large baking potatoes (about 2-1/2 pounds), peeled and thinly sliced
4 ounces tender young fresh sorrel leaves, rinsed and shredded
Salt and freshly ground black pepper to taste
1 cup milk
1 cup half-and-half
3 large eggs
1-1/2 cups freshly grated Parmesan cheese

1. Preheat the oven to 325°F. Butter a 2-quart casserole and set aside.

2. In a medium-size skillet, melt the butter over moderate heat, add the mushrooms and garlic, stir till softened, about 3 minutes, and remove from the heat.

3. Layer half the potatoes overlapping over the bottom of the prepared casserole, spoon the mushrooms evenly over the potatoes, and sprinkle the sorrel over the mushrooms, Layer the remaining potatoes overlapping over the top and season generously with salt and pepper.

4. In a large mixing bowl, whisk together the milk, half-and-half, and eggs till well blended, pour over the casserole, and bake for 1 hour. Sprinkle the cheese evenly over the top and continue to bake till golden brown, about 30 minutes, basting once or twice and not allowing the casserole to get too dry.

Makes 6 servings.