1 cup (250 ml) uncooked white rice
2 cups (500 ml) chicken stock
2 tablespoons (30 ml) olive oil
1 pound (450 grams) chicken breasts, cut into bite-size pieces
1 pound (450 grams) baby spinach
1 cup (250 ml) mushrooms, roughly chopped
1 onion, diced
1 cup (250 ml) Monterey Jack cheese
Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius).
In a large oven-safe skillet, add the white rice and the chicken stock. Season with salt, cover with a lid and bring to a boil. When boiling, reduce heat to low and simmer until the rice has completely absorbed the liquid, about 10 minutes. Fluff with a fork and then set aside in a large bowl.
In the same skillet set over medium heat, heat the olive oil. Add the chicken, season with salt and pepper, and cook for about 10 minutes, until chicken is cooked through, stirring regularly. Add to the bowl with the rice.
Place the skillet back over medium heat and, if it's running dry, add more olive oil. Add the onion and mushrooms and cook, stirring regularly, until vegetables are soft and mushrooms are just starting to brown. Add the spinach and cook just until wilted. Season with salt and pepper and pour contents of bowl back into the skillet.
Stir ingredients together to combine well and sprinkle with Monterey Jack cheese.
Place in the preheated oven and cook for 20 - 30 minutes, until cheese is melted and casserole is hot and bubbling throughout.