Bring a large pot of salted water to a boil. Add the orzo and cook until al dente. Just before draining, reserve one cup of pasta water and set aside.

In a large skillet, melt the butter over medium heat. Add the mushrooms and salt. Sauté for 5-7 minutes until browned.

Add the garlic and shallot and cook for 2-3 more minutes.

Remove the mushrooms from heat. Add the reserved pasta water and Parmesan, stirring until smooth and creamy.

Add the cooked orzo, baby spinach, and lemon juice and stir until combined and creamy.

Season with black pepper and salt to taste. Serve with additional Parmesan cheese, if desired.