This lasagna is so delicious, even if it is a bit labor intensive. You can prepare some steps ahead; you can even assemble the lasagna ahead of time and refrigerate or freeze it for when you want to eat it. This was adapted from a Food Network magazine recipe.
Some notes you may find helpful, before you begin:
1) The original recipes calls for 1 1/2 lbs of shiitake mushrooms. I was being frugal and substituted white button mushrooms at a savings of about $10.
2) I wasn’t so frugal when it came to the tomatoes and the mozzarella though. The San Marzano whole peeled tomatoes may cost about $1 or $2 more per can but worth it; you can really taste the difference in the quality of the sauce. Also, instead of buying shredded mozzarella (in the refrigerated section), I bought a 1 1/2 lbs of fresh, salted mozzarella (in the deli section) and shredded it myself.
3) It takes a while for frozen chopped spinach to thaw, so start that ahead of time. I don’t have a microwave, so if there’s a trick to faster thawing using a microwave, I don’t know it. I put the spinach in a colander with a bowl underneath and let it thaw out naturally. Then I placed the spinach in a clean dish towel and squeezed all the excess liquid from it.
4) I used a 9×13 baking dish, but mine was not deep enough. Of course, I realized this after I had already laid down one layer. So I assembled one and a half layers in my baking dish and was able to assemble another lasagna in an 8×8 baking dish that I wrapped in plastic wrap, then aluminum foil and put in the freezer for another night. If you freeze the lasagna unbaked, defrost in the fridge than follow the baking directions below.
Spinach Lasagna with Mushroom Ragu
For the ragu:
1 oz dried porcini mushrooms
2 tbsp extra virgin olive oil
1 medium onion, finely chopped
1 large carrot, finely chopped
1 stalk celery, finely chopped
4 cloves garlic, chopped
2 tbsp tomato paste
2 portobello mushroom caps, chopped
1 1/2 lbs white button mushrooms, chopped
Sea salt and freshly ground pepper
2 28-oz cans whole peeled San Marzano tomatoes, crushed by hand (I used a potato masher)
2 cups water
Soak the porcini mushrooms in 1 cup hot water until soft, about 15 minutes. Strain, but reserve the liquid.
Meanwhile, heat the olive oil in a large pot over medium heat. Add the onion, carrot and celery and cook until soft, about 7 minutes.
Stir in the garlic and tomato paste and cook, stirring frequently, for a couple minutes.
Add the portobello and white button mushrooms, 1 tsp salt and freshly ground black pepper. Cook, stirring occasionally, until the mushrooms are soft, about 5 minutes. Add the porcini mushrooms and cook for a couple of minutes before adding the reserved liquid. Bring to a boil and cook until slightly reduced, about 3 minutes.
Add the tomatoes and their juice and the water. Bring to a boil, stirring occasionally. Reduce the heat to medium low, add 1 tsp of salt, and simmer, stirring occasionally, until thick. This will take about an hour and a half.
For the lasagna:
3 oz grated parmesan cheese
1 1/2 lb mozzarella, shredded
8 oz asiago cheese, shredded
2 lbs ricotta cheese
2 large eggs, lightly beaten
1 lb frozen chopped spinach, thawed and squeezed dry
12 oz dried lasagna noodles
Mix the parmesan, mozzarella, and asiago cheeses. Set 1 1/2 cups of this mixture aside.
Into the remaining cheese mixture, combine the ricotta, eggs, spinach and 1/2 tsp salt.
Preheat the oven to 375 degrees. Bring a large pot of salted water to a boil and cook the lasagna noodles according to the package directions. Drain and rinse under cold water. Shake off the excess water. I laid the noodles flat on a baking sheet that had been sprayed with cooking spray to keep from sticking.
Spread a cup of the ragu in the baking dish. Add a layer of noodles, then half of the spinach mixture on top of the noodles, and 2 cups of ragu on top of the spinach mixture. Repeat the same layering. Top with the remaining noodles and ragu and sprinkle the top with the cheese mixture that was set aside.
Cover with foil and place the baking dish on top of a baking sheet. Bake for about 50 minutes covered. Then uncover and bake until golden, about 25 more minutes. Let rest for about 10 minutes before serving.