Step 1

Preheat the oven to 400 degrees F.

Step 2

In a large, high-sided skillet over medium-high heat, add the oil.

Step 3

Add the chicken pieces and the chopped onions to the hot oil and cook, stirring occasionally, until the meat reaches an internal temperature of 165 degrees F, about 7 minutes.

Step 4

Evenly sprinkle the flour over the chicken mixture and cook, stirring occasionally, about 1 minute.

Step 5

Add the milk to the chicken mixture and bring it to a boil, stirring frequently.

Step 6

Boil the chicken mixture, stirring constantly, about 1 minute.

Step 7

Transfer the skillet from the heat. Carefully stir the cooked rice, the cooked broccoli florets, the cheese, the dry mustard, the garlic powder, the salt, and the pepper into the chicken mixture.

Step 8

Evenly sprinkle the chicken mixture with the crispy fried onions.

Step 9

Bake the chicken casserole until the edges are bubbling, about 10 minutes.

Step 10

Transfer the skillet to a wire rack and let the chicken casserole rest, about 5 minutes.

Step 11

Serve.