Golden Gruyere, Spinach And Mushroom Lasagna

• 2 tablespoons vegetable oil or 2 tablespoons extra virgin olive oil
• 3/4 lb white mushrooms or 3/4 lb button mushroom, sliced
• 1/2 onion, finely diced
• 1 (10 ounce) package cut-leaf frozen spinach
• 3 cups 2% low-fat milk, plus more as needed
• 1/4 cup butter
• 1/4 cup flour, plus
• 1 tablespoon flour
• 1/2 teaspoon salt
• fresh ground pepper, freshly ground nutmeg
• 4 ounces ham, cut into roughly 1/4-inch dice
• 1/2 lb gruyere cheese (or a combination of the two) or 1/2 lb emmenthaler cheese, grated (or a combination of the two)
• 3/4 lb fresh no-boil lasagna sheets or 3/4 lb cooked lasagna sheet, prepared according to package directions

1. Heat 1 tablespoon of oil in a large saucepan over medium-high heat. Add mushrooms; cook, stirring, until they begin to brown and any moisture has evaporated. Transfer to a large plate to cool.
2. Heat the remaining tablespoon of the oil in the same pan over medium-high heat. Add the onion; cook until soft, 3-4 minutes. Add the frozen spinach; cover. Cook 2 minutes; remove the lid. Stir the spinach. Cover; repeat until the spinach is thawed. Remove cover; cook until the moisture from the spinach has evaporated. Transfer the spinach-onion mixture to a large plate to cool.
3. Heat milk; set aside. Melt butter in a large heavy saucepan over medium heat; stir in flour. Cook, stirring, until mixture starts to thin, 1-2 minutes. Add warm milk in a steady stream while whisking mixture. Add salt, pepper and nutmeg to taste. Heat to a boil; reduce heat to low. Simmer sauce, stirring often until sauce coats the back of a spoon, 10 minutes. Stir in ham; remove from heat. Add three-fourths of the cheese; stir until it melts. Set aside.
4. Spoon a few tablespoons of the bechamel-cheese sauce in a 13-by-9-inch pan. Cover the sauce with a layer of lasagna sheets. Spread the spinach-onion mixture over the first layer; cover with one-third of the sauce. Add another layer of lasagna sheets; spread the mushrooms over this layer. Cover with one-third of the sauce. Add the last layer of lasagna sheets; spread the remaining sauce over. Top with the remaining grated cheese. Cover; refrigerate until baking time, up to 12 hours. Or wrap well and freeze.
5. Heat the oven to 350 degrees. Bake lasagna, uncovered, until heated through and the cheese is golden brown, 35-45 minutes. (If frozen, the lasagna should be baked, covered with foil, 45 minutes, then uncovered and baked until heated through, 30-40 minutes.).

vegetable oil, white mushrooms, onion, frozen spinach, milk, butter, flour, flour, salt, fresh ground pepper, ham, gruyere cheese, fresh noboil

Taken from www.food.com/recipe/golden-gruyere-spinach-and-mushroom-lasagna-151224 (may not work)