Bring a large pot of water to a boil.

Add pasta and cook according to package directions.

Drain and set aside.

Overhead view of all ingredients in various bowls for Creamy Chicken, Mushroom & Spinach Skillet Casserole recipe

Photographer: Rachel Marek, Food Stylist: Annie Probst

Meanwhile, heat 2 tablespoons oil in a large ovenproof skillet over medium heat.

Add onion; cook, stirring, until softened, about 2 minutes.

Add garlic; cook, stirring, for 1 minute.

Overhead view of a skillet of mushrooms, onions, garlic and oil cooking in oil for Creamy Chicken, Mushroom & Spinach Skillet Casserole recipe

Photographer: Rachel Marek, Food Stylist: Annie Probst

Transfer the mixture to a large bowl.

Add the remaining 1 tablespoon oil to the pan.

Sprinkle in flour; cook, stirring, for 1 minute.

Overhead view of a skillet after adding all ingredients for Creamy Chicken, Mushroom & Spinach Skillet Casserole recipe

Photographer: Rachel Marek, Food Stylist: Annie Probst

Gradually add milk and mustard; cook, whisking constantly until the sauce thickens, 2 to 3 minutes.

Remove from heat and stir in 1/2 cup Parmesan and the remaining 1/4 teaspoon each salt and pepper.

Add the pasta, chicken, spinach and the mushroom mixture.

Overhead view of a skillet of Creamy Chicken, Mushroom & Spinach Skillet Casserole recipe

Photographer: Rachel Marek, Food Stylist: Annie Probst

Stir until well coated.

Smooth the top and sprinkle with the remaining 1/4 cup Parmesan.

Bake until bubbling, about 15 minutes.

  • Daily Values (DVs) are the recommended amounts of nutrients to consume each day.

(-) Information is not currently available for this nutrient.