Preheat the oven to 350 degrees F (176 degrees C).
Place the Boneless, Skinless Chicken Breast (4) in a 9x13-inch casserole dish and season it generously with the Salt (3 pinch), Ground Black Pepper (3 pinch), and Garlic Powder (3 pinch).
Evenly distribute the Cremini Mushroom (8 ounce) and Long Grain White Rice (1 cup) over and around the chicken, then pour in the Avocado Ranch Dressing (3 cup) and Chicken Stock (1 cup). Finally, sprinkle the Grated Parmesan Cheese (1/4 cup) evenly on top.
Bake the casserole for 1 hour, taking it out and stirring the rice every so often.
When the casserole is done, place the Avocado (to taste) on top and serve immediately!