How to Make It
Prepare pasta in a large stockpot according to package directions, omitting salt and fat. Drain pasta, reserving 1/4 cup cooking liquid. Return pasta and reserved cooking liquid to stockpot.
Heat oil in a large saucepan over medium-high. Add spinach and garlic; cook, stirring often, until spinach wilts and garlic is slightly softened, about 3 minutes. Add fontina, ricotta, and cream cheese; cook, stirring constantly, until cheeses melt and mixture is creamy, about 30 seconds. Immediately remove from heat; add to pasta in stockpot. Add salt and cayenne. Stir gently to coat pasta with sauce.
Divide pasta among 4 bowls; top with Parmesan. Serve immediately.