Heat a large skillet over medium high heat and add 1 tablespoon of the butter and add half the mushrooms. Cook for about 7-10 minutes, until mushrooms are browned and have released their liquid.
Do the same process with the second batch of mushrooms.
Preheat the oven to 375F degrees.
Sauté the shallots and garlic in the same pan the mushrooms were cooked in until soft. Toss them with the mushrooms.
Place a layer of bechamel sauce in the bottom of a 8x13" baking dish. Add a layer of noodles.
Add the sliced tomatoes and half of the mushrooms. Add dollops of ricotta cheese and mozzarella over the mixture and sprinkle with Romano.
Cover with another layer of noodles and spread a light layer of bechamel sauce over the top.
Add the second half of the mushrooms and dollop with the ricotta cheese, then sprinkle with Romano.
Add the last layer of noodles. Top with the remaining bechamel sauce and sprinkle with the Mozzarella cheese.
Cover with aluminum foil and bake in the oven for 45 minutes. Remove foil and bake an additional 15 minutes uncovered.
Remove from oven and let cool for 10-15 minutes. Slice and serve.
Bechamel Sauce
Heat the butter in a saucepan until melted and add the flour, whisking constantly for 2-3 minutes.
Add the milk, a little at a time, whisking constantly, until a sauce is formed.
Remove from heat and stir in the nutmeg, salt and pepper. Set the béchamel sauce aside while you prepare the remaining ingredients.
Notes
The mushrooms must be cooked before adding them to the lasagna - otherwise there will be too much moisture.
Two skillets can be used to cook the mushrooms to save time.
Uncovering the lasagna during the last 15 of baking allows the cheese to brown on top.
Be sure to whisk constantly when adding the milk to the bechamel sauce to keep it from getting lumpy. Add the milk SLOWLY.