Creamy Chicken and Mushroom Casserole

1 . Stage

Preheat the oven to 325 degrees F (165 degrees C).

2 . Stage

Bring a large pot of lightly salted water to a boil; cook rotini at a boil until tender yet firm to the bite, about 8 minutes. Drain pasta and reserve 1/2 cup cooking liquid.

3 . Stage

Heat oil in a large Dutch oven over medium heat. Add onion, celery, and bell pepper; sauté until onion is translucent, 5 to 7 minutes. Stir in mushrooms. Sprinkle flour over vegetables and stir until mixture becomes paste-like and light golden brown, 2 to 4 minutes. Add broth; cook and stir until mixture begins to thicken, 2 to 3 minutes. Reduce the heat to low, cover, and cook for 10 minutes. Stir in condensed soup and reserved 1/2 cup cooking liquid, then stir in chicken and peas.

4 . Stage

Add pasta to the Dutch oven and stir until well combined. Transfer mixture to an 11x7-inch baking dish and sprinkle Parmesan cheese over top.

5 . Stage

Cover and bake in the preheated oven for 20 minutes. Uncover and continue to bake for 5 more minutes.