Cook the pasta: Bring a large pot of salted water to a boil. Cook rigatoni until al dente according to package instructions. Reserve 2 cups of pasta water before draining.

Cook the sausage: While pasta cooks, heat olive oil in a large skillet over medium heat. Add sausage and break it apart with a wooden spoon. Cook until browned and no longer pink. Remove and set aside, leaving fat in the pan.

Sauté the vegetables: In the same skillet, add onions and cook for 3–4 minutes until softened. Add mushrooms and cook until tender and lightly browned, about 5 minutes. Add garlic and cook for 30 seconds until fragrant.

Deglaze the pan: Pour in the white wine and scrape up any browned bits from the bottom of the pan. Simmer until the wine has reduced by half, about 2–3 minutes.

Make the sauce: Reduce heat to low. Stir in the heavy cream and a pinch of nutmeg. Return the sausage to the pan. Simmer gently for 5–7 minutes until slightly thickened. If sauce is too thick, add reserved pasta water, a little at a time, to reach desired consistency.

Combine and finish: Add the cooked pasta and Pecorino Romano to the sauce. Toss to coat thoroughly. Adjust seasoning with salt and pepper to taste.