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Ligurian Potato, Green Bean and Mushroom Gratin

Ligurian Potato, Green Bean and Mushroom Gratin

  • Makes
    8 servings
  • Cook Time
    1 hour 20 minutes
  • Active time plus cooling
    50 minutes active, plus cooling
  • Rating

Polpettone alla Ligure is the Italian name for this rustic, oven-baked dish. The term polpettone translates as “meatloaf,” but in this case, it refers to a mashup of vegetables baked into a casserole. In classic versions, the potatoes are cooked and pureed before cooked green beans, eggs and Parmesan cheese are mixed in. After baking, the vegetables are set enough to be cut into neat squares. For a more satisfying texture, we keep the potatoes on the chunky side, and for added savoriness, we supplement the beans with cremini mushrooms. Just before slipping the baking dish into the oven, we top the vegetables with a mixture of panko breadcrumbs and Parmesan for toasty crispness. If convenient, 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 of almost any type.

Tip

Don’t overcook the mushrooms and beans when sautéing them, as they will continue to cook in the oven. Sauté the mushrooms until they give up their moisture and the beans are bright green but still quite crisp; they should not be browned.

Ingredients
  • 4

    tablespoons (½ stick) salted butter, plus 2 tablespoons salted butter, melted

  • 1

    pound Yukon Gold potatoes, peeled and sliced ¼ 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 ¼-inch pieces

  • 8

    ounces cremini mushrooms, trimmed and sliced about ¼ inch thick

  • 1

    tablespoon minced fresh marjoram or oregano

  • 2

    large eggs

  • 3

    ounces Parmesan cheese, finely grated (1½ cups), divided

  • ½

    cup panko breadcrumbs

Step 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 ½ teaspoon salt, then stir to coat. Add ½ 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.

Step 2

Wipe out the skillet and set it over medium. Add the oil, shallots and ¼ 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.

Step 3

In a medium bowl, whisk the eggs, 2 ounces (1 cup) of Parmesan, ½ 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.

Step 4

In a small bowl, combine the panko, the melted butter and the remaining 1 ounce (½ 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.

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