Preheat your oven to 350 degrees.
Prepare your rice according to package directions, substituting chicken broth for the water.
Place a skillet over medium-high heat. When the pan is hot, add olive oil and vegetables. Saute until the vegetables are softened.
Meanwhile, melt the butter in a small pot. Stir in the flour and salt. Next, slowly pour in the milk and/or chicken broth. (I use about a cup of each.) Whisk well and when it starts to bubble and thicken, remove it from the heat.
Pour the sauce into your skillet with vegetables. Add the chicken, black pepper, and thyme. When the mixture bubbles, stir in your cooked rice and remove it from the heat.
Transfer the rice mixture into a casserole dish. Sprinkle with cheese and chow mein noodles, if desired, for crunch.
Heat in the oven until the cheese has melted, about 20 to 30 minutes.