Season 5 of Christopher Kimball's Milk Street Television airs Saturdays at 3:00 pm.
Green bean casserole has become a classic Thanksgiving side dish, thanks to the easy recipe dreamed up by Dorcas Reilly for the Campbell Soup Company in 1955. But in case you wanted to try something different, with more fresh ingredients, than the green bean-cream of mushroom soup-fried onion casserole, Milk Street has this hearty Italian version that's filled out with mashed potatoes and fresh mushrooms. There are no French's onions in sight, but shallot does add some extra oomph.
Ligurian Potato, Green Bean, and Mushroom Gratin
Polpettone alla Ligure is the Italian name for this rustic dish. The term polpettone translates as “meatloaf,” but in this case, it refers to a mashup of vegetables baked into a casserole. Before baking, we top the vegetables with a mixture of panko and Parmesan for toasty crispness; after baking, the vegetables are set enough to be cut into neat squares. The gratin can be assembled, covered, and refrigerated for up to six hours before baking, but keep the panko mixture separate. Just before baking, sprinkle with the topping and extend the cooking time by about 15 minutes. With a salad alongside, this dish is a satisfying vegetarian main, or offer it as a side to braises or roasts.
Don’t overcook the mushrooms and beans when sautéing them, as they will continue to cook in the oven. Sauté until the mushrooms give up their moisture and the beans are bright green but still quite crisp; they should not be browned.
4 tablespoons (1⁄2 stick) salted butter, plus 2 tablespoons salted butter, melted
1 pound Yukon Gold potatoes, peeled and sliced 1⁄4 inch thick
Kosher salt and ground black pepper
3 tablespoons extra-virgin olive oil
2 medium shallots, finely chopped
1 pound green beans, trimmed and cut into 1⁄4-inch pieces
8 ounces cremini mushrooms, trimmed and sliced about 1⁄4 inch thick
1 tablespoon minced fresh marjoram or oregano
2 large eggs
3 ounces Parmesan cheese, finely grated (1 1⁄2 cups), divided
1⁄2 cup panko breadcrumbs
1. Heat the oven to 400°F with a rack in the middle position. Mist a 9-by-13-inch baking dish with cooking spray and set aside. In a 12-inch skillet over medium, melt 4 tablespoons butter. Add the potatoes and 1⁄2 teaspoon salt, then stir to coat. Add 1⁄2 cup water, then distribute the potatoes evenly. Cover and cook until a skewer inserted into the potatoes meets no resistance, 15 to 20 minutes, stirring once about halfway through. Transfer the potatoes and any liquid in the pan to a large bowl, then use a fork to mash to the consistency of chunky mashed potatoes; set aside.
2. Wipe out the skillet and set it over medium. Add the oil, shallots, and 1⁄4 teaspoon salt. Cook, stirring occasionally, until the shallots are softened but not browned, 5 to 6 minutes. Add the beans and mushrooms, then increase to medium-high. Cook, stirring occasionally, until most of the liquid released by the mushrooms has evaporated and the beans are bright green but still crisp, about 5 minutes; the vegetables should not begin to brown. Stir in the marjoram and cook until fragrant, about 30 seconds. Transfer to the bowl with the potatoes and cool for about 10 minutes.
3. In a medium bowl, whisk the eggs, 2 ounces (1 cup) of Parmesan, 1⁄2 teaspoon each salt and pepper. Add the egg mixture to the vegetable mixture and fold with a silicone spatula until combined. Transfer to the prepared baking dish and spread evenly.
4. In a small bowl, combine the panko, the melted butter, and the remaining 1 ounce (1⁄2 cup) Parmesan, then stir until the panko is evenly moistened. Sprinkle evenly over the vegetables. Bake until golden brown and bubbling at the edges, about 30 minutes. Cool for about 15 minutes before serving.