In a large, deep-sided skillet over medium-high heat, cook sausage, crumbling with a wooden spoon until beginning to brown, about 5 minutes. Add carrot, celery, onion, and garlic, and cook until tender, another 5 minutes. Add sauce and let simmer for 5 minutes, then season with salt and pepper.
Meanwhile, in a separate skillet, heat olive oil over medium-high heat and cook kale until wilted, 3 minutes. Season with salt and pepper, then move to a strainer and press down with paper towels to squeeze out any excess liquid.
In a large bowl, stir together ricotta, Parmesan, and egg. Season with salt and pepper and a pinch of nutmeg, then stir in wilted kale.
Spread a few spoonfuls of sauce in the bottom of a small, deep-sided square or rectangular baking dish. Layer with 3 noodles and cover with 1/3 ricotta mixture.
Add 1/3 mozzarella and cover with sauce; repeat layers two more times, ending with mozzarella on top.
Cover with aluminum foil and bake for 15 to 20 minutes. Heat broiler; cook for 2 minutes or until cheese is bubbling and brown on top. Let cool slightly, then garnish with chopped parsley and serve.