01 - Boil salted water in a large pot and cook pasta al dente according to package directions. Reserve 1/2 cup pasta water, then drain and set aside.
02 - Heat olive oil in a large skillet over medium heat. Add chopped onion and sauté for 2 to 3 minutes until softened.
03 - Add minced garlic and sliced mushrooms to the skillet. Cook for 6 to 8 minutes, stirring occasionally, until mushrooms are golden and moisture has evaporated.
04 - Add fresh spinach and cook for 1 to 2 minutes until wilted.
05 - Lower heat to low, then stir in heavy cream, vegetable broth, thyme, black pepper, and salt. Simmer gently for 2 to 3 minutes.
06 - Add grated Parmesan cheese and stir until melted and sauce is smooth. Adjust thickness by adding reserved pasta water gradually if needed.
07 - Add cooked pasta to the skillet and toss to coat evenly. Heat for 1 to 2 minutes, adjusting seasoning as required.
08 - Plate immediately and garnish with extra grated Parmesan cheese and freshly ground black pepper.