Chicken and Peas Au Gratin Casserole

2 tablespoons olive oil

3 cups cubed skinless, boneless chicken

4 cups torn bread pieces

1 cup shredded Cheddar cheese

¼ cup butter, melted

2 cups frozen peas

¼ cup butter

½ cup all-purpose flour

3 cups milk

2 teaspoons salt

½ teaspoon black pepper

Preheat an oven to 350 degrees F (175 degrees C).

Heat the olive oil in a skillet over medium heat. Cook the chicken until no longer pink in the center and the juices run clear, 5 to 7 minutes; drain and set aside.

Toss the bread pieces, Cheddar cheese, and 1/4 cup melted butter together in a bowl; spread about half of the mixture into the bottom of a 9x13-inch baking dish. Layer the peas and chicken atop the bread layer.

Melt 1/4 cup butter in a saucepan over medium heat; stir the flour, milk, salt, and pepper into the melted butter. Cook and stir the sauce until smooth and thick, 5 to 7 minutes. Pour over the casserole. Top with the remaining bread mixture.

Bake in the preheated oven until the top begins to brown, 30 to 40 minutes.