Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish using butter or nonstick spray.
Arrange the lasagna noodles in a separate 9x13-inch pan or a comparable long and shallow dish and submerge them in hot water for a minimum of 30 minutes.
In a large skillet over medium-high heat, add butter and chopped onion, cooking until translucent (about 10 minutes).
Incorporate minced garlic and cook for an additional 2 minutes.
Add fresh baby spinach to the skillet and cook until wilted.
Stir in heavy cream, dried basil, salt, and pepper, bringing the mixture to a simmer.
Add Parmesan and ricotta cheeses, stirring until melted, then integrate shredded chicken and remove from heat.
Spread a spoonful of the Alfredo sauce mixture across the bottom of the prepared baking dish, then layer with pre-soaked noodles.
Apply one-third of the Alfredo sauce mixture and one-third of the grated mozzarella cheese on top, repeating the layering process until all ingredients are used.
Cover the baking dish with foil and bake for 45 minutes, then optionally broil for 2-3 minutes for a browned cheese topping.
Allow the lasagna to rest for 10 minutes before serving, optionally garnishing with minced fresh parsley.