1. Heat a large pot over medium-high heat and add the butter or oil. Once hot, add the mushrooms, onion, and garlic. Season lightly with salt and pepper. Cook, stirring occasionally, until the mushrooms release their moisture and turn golden, about 7–8 minutes. Transfer the vegetables to a bowl and set aside.

2. In the same pot, add the ground beef. Season with salt and pepper and cook, breaking it apart, until fully browned and no longer pink, about 5–8 minutes.

3. Return the mushroom mixture to the pot and stir in the spinach. Cook just until the spinach wilts.

4. Pour in the milk and broth, stirring to combine. Add the uncooked noodles and bring to a gentle boil.

5. Reduce heat slightly and cook, stirring often, until the noodles are tender and most of the liquid is absorbed, about 10–12 minutes. You want a small amount of liquid left for a creamy sauce. If needed, add up to 1/2 cup extra broth near the end.

6. Remove from heat and stir in the mozzarella and Parmesan until melted and creamy. Taste and adjust seasoning with additional salt and pepper if needed. Serve warm.