Boil the ravioli: Bring a large pot of salted water to a boil. Add ravioli and cook until just tender and floating, 2–4 minutes for fresh or per package if frozen. Reserve at least 1/2 cup pasta water. Drain and set aside.
Brown the mushrooms: Heat olive oil and 2 tablespoons butter in a large skillet over medium-high heat. Add mushrooms in an even layer. Let them sear without stirring for 3–4 minutes. Stir and continue cooking until golden and reduced, 6–8 minutes more.
Build the flavor base: Add garlic, thyme, and red pepper flakes. Cook 1 minute, stirring, until fragrant.
Deglaze and reduce: Pour in white wine. Scrape up browned bits. Simmer until reduced by half, 2–3 minutes.
Creamy finish: Reduce heat to medium-low. Stir in cream and the remaining 2 tablespoons butter. Simmer gently 2 minutes until slightly thickened.
Emulsify the sauce: Add Parmesan and a splash of reserved pasta water. Stir until the sauce turns glossy. Add more pasta water as needed to loosen.
Toss in ravioli: Add drained ravioli to the skillet. Gently fold to coat without tearing. Warm 1 minute.
Brighten: Stir in lemon zest, lemon juice, and parsley. Taste and season with salt and pepper. Add spinach now if using; wilt 30 seconds.
Serve: Plate with extra Parmesan, herbs, and nuts if you like. Add a tiny drizzle of truffle oil to make it extra special.
