Heat a cooking spray coated frying pan over medium heat. Cook mushrooms, onions, bell pepper, and garlic 3 minutes. Mix in spinach and artichokes. Place lid on pan, and sauté 5 minutes or until spinach is wilted. Continue cooking without lid until all liquid is evaporated. Take off of heat and sprinkle with salt and pepper.
To make sauce, pour 2 cups of milk in a pot and bring to a boil. Whisk together 1 cup milk and flour and whisk into boiling milk. Boil 1 minute, whisking continually until mixture is thick. Take off of heat and stir in Parmesan, cream cheese, parsley, thyme, and lemon juice, whisking until cream cheese is melted. Sprinkle with salt and pepper.
Spoon 1/2 cup sauce onto the bottom of a 13 x 9 inch baking pan. Lay 4 noodles, overlapping on sauce. Spread 1/2 of artichoke mixture over noodles and top with 1 cup sauce. Continue on with process finishing with noodles and sauce. Top with mozzarella cheese.
Bake, covered 45 minutes. Let rest 10 minutes before serving.