From here.

Ingredients

• 2 (12-ounce) bags frozen artichoke hearts
• 2 tablespoons olive oil, plus more for the baking dish
• 4 large bunches Swiss chard (about 3 pounds total), stems chopped into 1-inch pieces, leaves coarsely chopped and reserved separately
• 1 teaspoon red pepper flakes
• 6 cloves garlic, minced
• 2 tablespoons red wine vinegar
• Kosher salt
• Freshly ground black pepper
• 2 (18-ounce) tubes cooked polenta, sliced into 1/4-inch-thick rounds
• 6 ounces grated Gruyère cheese (about 1 1/2 cups), divided
• 1/2 cup grated Parmesan cheese

Method

Arrange a rack in the top third of the oven and heat to 400°F. Lightly coat a 9x13-inch baking dish with olive oil; set aside. Place the frozen artichoke hearts in a colander and run cold water over them for a few seconds to slightly defrost. Gently pat dry, coarsely chop them into bite-size pieces, and set aside. Heat the 2 tablespoons of olive oil in a large skillet over medium heat until shimmering. Add the Swiss chard stems and red pepper flakes and sauté until tender, about 4 minutes. Add the Swiss chard leaves, garlic, and vinegar and sauté until the leaves are just wilted, about 1 to 2 minutes more. Stir in the chopped artichokes and season with salt and pepper. Spread the mixture evenly in the prepared baking dish. Sprinkle with 1 cup of the Gruyère. Lay the polenta rounds over the filling, overlapping them slightly as you go. Sprinkle the remaining 1/2 cup Gruyère and Parmesan over the top. Bake until heated through and cheese is bubbling, about 15 minutes. Increase the oven temperature to broil and broil until the top is lightly browned, 3 to 4 minutes more. Let cool 5 minutes before serving.