Preheat the oven to 375º F.
Bring a large pot of water to a boil and add one tablespoon each of salt and olive oil. Add the lasagna noodles and cook for fifteen minutes. Drain and set aside.
To prepare the white sauce, bring four cups of milk to a simmer in a saucepan. Set aside.
Melt eightt ablespoons of the butter in a large sauce pan. Add one-half of a cup of Bisquick and cook for one minute over low heat, stirring constantly.
Pour the hot milk into the butter-flour mixture and add one teaspoon each of pepper and nutmeg. Cook over medium-low heat, stirring with a whisk for five minutes oruntil thick. Remove from the heat and set aside.
Cut the mushrooms into thick slices. Heat two tablespoons of oil and two tablespoons of butter in a large skillet. When the butter has melted, add half of the mushrooms, sprinkle with salt, and cook over medium heat for approximately five minutes or until the mushrooms are tender.
Repeat with the remaining mushrooms. Remove the pan from the heat and set it aside.
To assemble the lasagna, spread enough of the white sauce to cover the bottom of a baking dish.
Arrange a layer of noodles on top, more sauce, one-third of the mushrooms, and one-quarter of a cup of grated Parmesan cheese.
Repeat two more times and sprinkle with the remaining Parmesan.
Bake the lasagna for forty-five minutes, or until nicely browned.
Allow the lasagna to cool for fifteen minutes before serving.