cook the gnocchi according to the package directions, reserving 1/4 cup of the cooking liquid. meanwhile, heat the oil in a large skillet over medium heat. add the onion and cook until softened, about 5 minutes. add the sausage and cook, crumbling it with a spoon, until browned, 5 to 7 minutes. add the garlic, spinach, salt, and pepper and cook, tossing frequently, until the spinach wilts, about 3 minutes. add the drained gnocchi, the reserved cooking liquid, and the parmesan and toss. sprinkle with additional parmesan.