For a crunchy topping, don't mix the almonds in with the other ingredients. Instead, sprinkle the almonds over the casserole 10 minutes before it's done baking.
1 can (4 ounces) mushroom stems and pieces, drained, can be substituted for the fresh mushrooms.
Tuna-Rice Casserole: Substitute 1 can (12 1/2 ounces) tuna, drained, for the chicken.
Turkey-Wild Rice Casserole: Substitute 2 cups cut-up cooked turkey for the chicken, and wild rice for the white rice.