Cook pasta al dente according to package instructions.
While the pasta is cooking, add the sausage and onion to a skillet and sauté over medium-high heat for 8-10 minutes until cooked through and nicely browned.
Reduce the heat to medium and stir in chopped garlic and mustard. Add white wine and cook for another minute or two just until the wine is reduced by half.
Turn off heat, add spinach and toss just until the spinach has wilted. Add pasta and toss to coat. Taste and season with salt and pepper as desired.
Transfer to serving bowls and top with freshly grated Parmigiano. Serve hot.