First, I removed the Italian sausage from the casing, crumbled it into a heavy bottomed skillet, and cooked it until most of the pink was gone. If you've worked much with Italian sausage, you know that it is hard to break it into small pieces. It looks something like this -
Here's one of my favorite tips - use a potato masher to break up the sausage into smaller pieces to finish cooking!
Remove the sausage from the pain and drain on paper towels. Next, cook onions, mushrooms, and garlic in a large dutch oven. (I used a mix of white mushrooms and shitakes, but any kind would be fine.)
Using a slotted spoon, remove the veggies from the pot and put aside. Now it is time to make a bechamel sauce which will take the place of the traditional tomato sauce. If you never made bechamel, don't worry - it is very easy. Take an equal amount of oil/butter and flour and cook for a few minutes. This is the same way you start a roux for gumbo. But you don't want the flour to brown at all. Add liquid slowly and keep stirring until the sauce starts to thicken. Many recipes call for only milk, but I used a combination of milk and beef broth in this case. Once all of the liquid has been incorporated, add the spinach and stir until it cooks down. Then add back the sausage and the sauteed veggies.
Now you are ready to start layering the lasagna in the pan. Start with some of the sauce on the bottom. Add pasta to fit the pan. (If you've used dry pasta, it works best it you boil it for 3 or 4 minutes to give it a head start before putting it in the lasagna.) Top with slice mozzarella and grated parmesan. Keep layering until you use up all of your ingredients. I used a 13 x 9 pan with three layers in order to get a thinner lasagna.
Bake in a 350 degree oven for about 45 minutes. You'll know it is done when you insert a knife in the center, and it comes out hot. (Or you can use a thermometer like I do. You want it to be at least 165 degrees in the middle.)
It is important to let it rest for a few minutes so that you don't have a soupy plate full of pasta when you cut it.
Sausage, Mushroom, and Spinach Lasagna
1 lb Italian sausage, removed from casing
2 Tbs olive oil, divided
2 cups mushrooms, chopped
1 medium onion, chopped
2 cloves garlic, minced
1/4 cup all purpose flour
2 cups beef broth
1/2 cup milk
1 4 oz bag of baby spinach
Salt and pepper, to taste
3/4 lb fresh pasta (or dry lasagna noodles, boiled for 3-4 minutes)
1 lb mozzarella, sliced
1 cup parmesan cheese, grated
Preheat oven to 350 degrees. In heavy skillet, break up sausage and cook until done. Drain on paper towel and set aside. In a dutch oven (or large saucepan), heat 2 Tbs. olive oil. Add onions and mushrooms and cook about 5 minutes over high heat or until veggies start to soften. Add garlic and cook for an additional minute. Use a slotted spoon and remove sauteed veggies from dutch oven. To the oil remaining in the pan, add the remaining 2 Tbs. of olive oil and the flour. Cook for 2-3 minutes over medium heat stirring constantly, but do not let it start to brown. Slowly add the milk and broth until the sauce is smooth and begins to thicken. Add the spinach and continue stirring until the spinach cooks down. Add the sausage and sauteed veggies back to the pan. Add salt and pepper to taste.
Coat a baking dish with cooking spray. Add about a half cup of the sauce to cover the bottom. Add a layer of pasta, followed by mozzarella and parmesan. Continue layering until you have used up all over your sauce, pasta, and cheese. I used a 13x9 pan and ended up with three layers, but you could use a smaller baking dish and have more layers.
Bake for 45 minutes, or until the top is brown and the sauce is bubbly. Remove from oven and let sit for about 15 minutes to allow the sauce to thicken.
