Melt 1 T butter in a large skillet with a tight fitting lid over medium high heat. Once the butter is melted, add the sausage.
Cook, breaking apart the meat, until it is browned and cooked through, about 5 minutes. Transfer the sausage to a plate.
Reduce the skillet heat to medium. Add the remaining 4 tablespoons butter. Once melted, add the squash and onion. Cook, stirring occasionally, until the squash is tender and golden. About 8-10 minutes.
Add the garlic, salt, pepper, sage, and nutmeg. Continue cooking until the garlic is softened and fragrant, about 1 additional minute.
Add 1 1/2 cups of broth and gnocchi to the skillet. Increase the heat to medium high. Stir in the gnocchi, then cover the pan.
Cook, covered, until the gnocchi is just tender, about 5 minutes.
Uncover and stir in the sausage. Stir in the spinach a handful at a time, allowing it to wilt.
Sprinkle with Parmesan and season to taste.