Preheat your oven to 375F and move the rack to the top third of the oven.
Take the sausage meat out of the casings and crumble it into a deep oven-safe skillet over medium-high heat and cook for 5 minutes.
Stir in the onions and continue cooking for another 5 minutes or until the sausage is browned and the onions have softened. Take the pan off the heat, tilt it, and spoon out excess fat.
Return the pan to the heat, then add in the garlic and wine and let it bubble for about 30 seconds.
Add in the cream and pesto, and stir until smooth.
Stir in the gnocchi, and let it heat through for 1-2 minutes. Don't let the sauce get too thick. Add a splash more cream if it's starting to thicken up a lot.
Take the skillet off the burner and stir in the spinach (I use two spoons and let it wilt a bit), then top with the mozzarella. Bake, uncovered, for 15 minutes. You can then broil to brown the cheese more if desired, but watch it carefully so it doesn't burn.
Let it sit for 5 minutes prior to serving. Sprinkle with the parsley and freshly grated parmesan if desired, and season with salt & pepper if needed.
