Spinach and Mushroom Lasagna with Tomato Sauce

This is from the America's Test Kitchen "Cover and Bake" cookbook. It's awesome. The only thing I did different is that I didn't use fresh basil (I used dried) and I didn't use as much cheese as it calls for. I bought as much cheese as it calls for, but holy crap, it's a lot, and I didn't use it all. Oh yeah, and I didn't buy curly-leaf spinach, because I couldn't find it, and my bag was only 9 oz. Okay, here goes.

Serves 6 to 8

Cremini mushrooms are particularly good in this dish, but any fresh mushroom is fine. Smoked mazzarella, Gruyere, or fontina can be substituted for the mozzarella and Pecorino Romano for the Parmesan. Also, 3 1/2 cups of your favorite prepared tomato sauce can be substituted for the sauce in this recipe. Feel free to substitute 3 cups of your favorite cooked vegetables (roasted, steamed, sauteed, grilled, or broiled) for the mushrooms and spinach.

5 tablespoons olive oil
1 (10-ounce) bag curly-leaf spinach, washed, stemmed, and chopped
Salt and ground black pepper
1 medium onion, minced
1 pound cremini or white button mushrooms, stems trimmed, brushed clean, and sliced thin
2 medium garlic cloves, minced or pressed through a garlic press
1 (28-ounce) can crushed tomatoes
2 tablespoons chopped fresh basil leaves
12 no-boil lasagna noodles from one 8 or 9-ounce package
1 pound mozzarella cheese, shredded (about 5 1/3 cups)
3 ounces Parmesan cheese, grated (about 1 1/2 cups)

1. Heat 1 tablespoon of the oil in a Dutch oven over medium heat until shimmering. Add the spinach in handfuls and cook, stirring, until the spinach is wilted, about 4 minutes. Season with salt and pepper; transfer the spinach to a colander. Gently squeeze any excess liquid from the spinach; set aside (the cooked spinach should measure about 1 1/2 cups).

2. Wipe the pot clean and add 2 more tablespoons oil; return the pot to medium heat until shimmering. Add the onion and saute until translucent, about 5 minutes. Add the mushrooms and saute until they have released their moisture and are golden, 8 to 10 minutes. Season the mushrooms with salt and pepper to taste; transfer to a bowl and set aside (the cooked mushrooms should measure about 1 1/2 cups).

3. Add the remaining 2 tablespoons oil and the garlic; return the pot to medium heat until the garlic is fragrant but not brown, about 30 seconds. Stir in the tomatoes; bring to a simmer and cook until thickened slightly, about 5 minutes. Stir in the basil and season with salt and pepper to taste. Pour the sauce into a large measuring cup and add enough water to make 3 1/2 cups.

4. Spread 1/2 cup of the sauce evenly over the bottom of a 9 by 13-inch baking dish (or a shallow casserole dish of similar size). Lay 3 of the noodles crosswise over the sauce, making sure they do not touch each other or the sides of the dish. Spread 1 cup of the prepared vegetables evenly over the noodles, 2/3 cup of the sauce evenly over the vegetables, and 1 1/3 cups of the mozzarella and 1/3 cup of the Parmesan evenly over the sauce. Repeat this layering of the noodles, vegetables, sauce, and cheeses twice more. For the fourth and final layer, lay the last 3 noodles crosswise over the previous layer and top with the remaining 1 cup tomato sauce, 1 1/3 cups mozzarella, and 1/2 cup Parmesan.

5. Adjust an oven rack to the middle position and heat the oven to 375 degrees. Lightly spray a large sheet of foil with nonstick cooking spray and cover the lasagna. Bake 25 minutes; remove the foil and continue baking until the top turns golden brown in spots, about 15 minutes. Cool for 10 minutes before serving.