- 2 T. butter
- 2 large leeks, white part only, thinly sliced (about 2 cups)
- 1 pound thick asparagus spears, trimmed, cut diagonally into 1-inch pieces
- 1 cup coarsely chopped shiitake mushrooms
- 1 tsp. chopped fresh thyme
- 4 cups chicken stock or vegetable broth
- 1½ cups heavy cream
- 1 bay leaf
- 2 T. all-purpose flour
- nonstick vegetable oil spray
- 1 9-ounce package no-cook lasagna noodles
- vegetable mixture
- 1½ cups finely grated Parmesan cheese
Melt 1 tablespoon butter in large, heavy skillet over medium heat. Add leeks and cook until translucent, stirring often. Transfer to medium bowl and set aside.
Melt remaining 1 tablespoon butter in same pan and add asparagus. Cook about 2 minutes, then add mushrooms and thyme, and cook about 2 more minutes, stirring often, until asparagus is crisp to tender. Add to bowl with leeks and toss to mix.
Using the same skillet, add broth, cream and bay leaf, and bring to a gentle boil over medium-high heat; boil until slightly thickened. Spoon 1/2 cup mixture into small bowl and whisk in flour, mixing well. Slowly add back to the skillet, whisking as you go. Continue boiling gently until sauce thickens, about 1 minute. Remove from heat. Discard bay leaf. Season to taste with salt and pepper.
Preheat oven to 350 degrees F. Coat a 9- by 13-inch baking dish with nonstick spray. Cover the bottom of the dish with a thin layer of sauce. Add a layer of noodles, a layer of asparagus-mushroom mixture (about one-third of it) and a layer of sauce. Top with 1/2 cup cheese. Repeat layers twice more.
Cover dish tightly with foil. Bake until noodles are tender, about 45 minutes. Then uncover and bake until sauce is bubbling and cheese begins to brown, 5 to 6 more minutes. Let stand at room temperature at least 5 minutes before serving.