Add the olive oil to skillet medium high heat. Add the onion, sauté for 5 minutes, and stir. Add the mushrooms, garlic, and Italian seasoning. Continue to cook, stirring for 5 minutes. Stir in the Dijon mustard and white wine. Let it bubble for a minute. Add gnocchi. Wait until it starts to bubble again, cover the pan and reduce the heat to medium-low. Stir in the spinach, cover the pan again, and cook for 3 minutes. Stir in the parmesan and season with salt & pepper. Give it a taste; gnocchi should be soft.