Bring a large pot of salted water to a boil. Cook mushroom ravioli according to package directions, usually 3 to 4 minutes for fresh or 5 to 7 minutes for frozen. Reserve 1/2 cup pasta cooking water before draining. Drain gently.

While pasta cooks, melt butter in a large skillet over medium heat. Add minced garlic and cook for 1 minute, stirring constantly, until fragrant but not browned.

Pour in heavy cream and chicken broth. Stir to combine and bring to a gentle simmer. Let bubble for 2 to 3 minutes, stirring occasionally, until sauce thickens slightly and coats the back of a spoon.

Stir in salt, black pepper, and nutmeg if using. Taste and adjust seasoning as needed.

Using a slotted spoon, transfer cooked ravioli directly into the skillet with sauce. Gently toss to coat each piece. If sauce is too thick, add reserved pasta water a tablespoon at a time to reach desired consistency.

Add fresh spinach and toss gently until just wilted, about 1 minute. Spinach should turn bright green and tender.

Remove from heat. Sprinkle grated Parmesan over the top and toss everything together one final time. Serve immediately, garnished with extra Parmesan and fresh herbs if desired.