Warm 2 T. of olive oil in a large skillet. Add the onion, green pepper, and celery. Cook for 5 minutes over medium heat.
Add the mushrooms, zucchini, and garlic, and cook for another 5 minutes. Add the thawed spinach and broccoli.
Add the nutmeg, salt and pepper. Cook for yet another 5 minutes.
For The Ricotta Filling
Combine and set aside.
For The White Sauce
Melt butter in a saucepan over medium heat. Whisk in flour and let cook 1-2 minutes. Whisk in milk and chicken stock. Cook until sauce just begins to thicken.
Add cream cheese, Parmesan cheese, and salt & pepper. Cook until all cheese is melted.
To Assemble The Lasagna
Spread 1/4 c. white sauce on the bottom of a 13 x 9 casserole dish. Top with 4 lasagna noodles. Top lasagna noodles with 1/3 of the ricotta filling, 1/3 of the veggie filling, and 1/3 of the remaining sauce. Repeat layers, ending with a final layer of white sauce. Sprinkle 1 1/2 c. mozzarella cheese over the top. Cover with foil and bake at 350 degrees for 45 minutes. Remove foil and bake for 10 – 15 minutes longer, until cheese is melted and sauce is bubbly. Remove from oven and let sit at least 5 minutes before slicing.