• Gather all ingredients and any tools you'll need, including a casserole dish.

Preheat Oven:

• Preheat the oven to 375°F (190°C) so it's ready when the lasagna is assembled.

Prepare Mushrooms:

• Place the sliced mushrooms in a casserole dish and toss with olive oil, garlic powder, salt, and pepper until evenly coated.
• Bake the mushrooms for about 10 minutes, then remove them and drain any excess liquid; set the mushrooms aside.

Assemble Lasagna:

• Spoon roughly half of the pasta sauce into the bottom of the empty casserole dish and spread into an even layer.
• Arrange 3–4 no-boil lasagna noodles over the sauce, breaking them to fit as needed, and press them down so they are covered with about 1/4 inch of sauce.
• Spread half of the cottage cheese over the noodles into an even layer.
• Distribute half of the baked mushrooms and half of the spinach over the cottage cheese.
• Sprinkle half of the shredded mozzarella and half of the grated parmesan evenly on top.
• Repeat the layers using the remaining sauce, noodles, cottage cheese, mushrooms, spinach, and cheeses to build the second layer.
• If desired, scatter the chopped walnuts over the top for added crunch.

Bake & Rest:

• Cover the casserole with foil and bake for 30 minutes to heat through and marry the flavors.
• Remove the foil and bake uncovered for an additional 15 minutes, until the top is bubbly and lightly golden.
• Let the lasagna rest for 5–10 minutes before slicing so it firms up and is easier to serve.