Preheat the oven to 350 degrees Fahrenheit, and spray a 9 x 13-inch baking dish with nonstick cooking spray.
Combine 15 ounces whole milk ricotta cheese, 4 ounces softened cream cheese, ¾ cup buffalo sauce, ¾ cup blue cheese dressing, ½ cup blue cheese crumbles, and ⅓ cup sliced green onions until smooth. Add about ⅓ cup to the bottom of the baking dish and spread evenly.
Season 3 cups cooked shredded chicken with ½ teaspoon salt and ¼ teaspoon ground black pepper.
Start layering the lasagna with enough of the 1 pound oven-ready lasagna noodles to evenly cover the bottom of the pan, followed by a layer of ⅓ of the seasoned chicken, ⅓ of the sauce, and about 1 cup of the 4 cups shredded mozzarella.
Repeat the layers twice more, ending with the remaining cheese on top. Not including the initial sauce on the bottom, you should end up with three layers of noodles, chicken, sauce, and cheese.
Cover tightly with aluminum foil and bake for about 40-45 minutes, until the center of the lasagna reaches 165 degrees Fahrenheit and the noodles are softened all the way through. Remove the foil and broil on HIGH for 2-3 minutes, until the cheese is browned on top.
Remove the lasagna from the oven and let it rest for 5-10 minutes before cutting and serving it.
Notes
Leftover Instructions
Fridge: Cover and refrigerate leftovers for up to 5 days. Reheat at 350°F until the center reaches 165°F, or microwave until warm.
Freezer: Assemble in a freezer safe dish, wrap tightly, and freeze for up to 3 months. Thaw overnight, then add 25 to 30 minutes to the baking time.
Make Ahead: Assemble up to 24 hours ahead and refrigerate. Add 5 to 10 minutes to the baking time if needed.