Melt the butter in a large saucepan over low to medium heat and cook the onion and garlic in the butter until tender, stirring frequently.
In a large bowl, mix together cream of chicken soup, sautéed onions and garlic mixture, sour cream, garlic powder, onion powder, oregano, basil, pepper, poultry seasoning, and 1/4 cup of shredded Parmesan cheese, and all of the cubed chicken.
In a 9x13 inch casserole dish start layering as follows: place 3 lasagna noodles at bottom of dish, and spread half of the chicken mixture over the noodles, 1/2 of the mushrooms, and 1/2 of the spinach. Sprinkle 1/4 cup of grated parmesan cheese and 1/4 cup of mozzarella over the top.
Create another layer by repeating above step.
Use last 3 noodles to cover the second layer, and spread the entire top of the lasagna with the remaining 1 1/2 cups of shredded mozzarella and remaining 1/4 cup of parmesan.
When the layering is completed, cover with aluminum foil, making certain that the foil is not touching the top of the lasagna, and bake for 25 minutes 350 degree F (175 degrees C).
Remove foil and continue baking, for another 15-20 minutes or until cheesee browns nicely.
Let stand 10 minutes before serving, so lasagna can set as cheese cools (I usually let it set overnight, to allow for easier cutting).
Sprinkle parsley over dish before serving.
(Can cut recipe in half and use a 8x8 pan as well. Freezes nicely!).