Leek and asparagus frittata

2 tablespoons (1/4 stick) butter 1 cup chopped leeks (white and pale green parts only) 1 12-ounce bunch thin asparagus, trimmed, cut on diagonal into 1-inch pieces (about 2 1/2 cups) 1 cup sliced stemmed shiitake mushrooms 8 large omega-3 eggs 1 cup diced Fontina cheese, divided 1/2 teaspoon salt 1/2 teaspoon ground black pepper 1/4 cup grated Parmesan cheese

Preheat broiler. Melt butter in heavy broilerproof 10-inch-diameter nonstick skillet over medium heat. Add leeks and sauté 4 minutes. Add asparagus and shiitake mushrooms, sprinkle lightly with salt, and sauté until tender, about 6 minutes. Whisk eggs, 3/4 cup Fontina cheese, 1/2 teaspoon salt, and 1/2 teaspoon pepper in medium bowl. Add egg mixture to skillet; fold gently to combine. Cook until almost set. Sprinkle remaining 1/4 cup Fontina cheese and Parmesan cheese over. Broil until frittata is puffed and cheese begins to turn golden, about 3 minutes. Cut into wedges and serve.

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