• In a large Dutch oven, or similarly sized soup pot, heat the olive oil over medium high heat.
• Add the vegetables, and saute them until tender- about 8 minutes. Add in the garlic, stirring to incorporate, and let it cook for 1 minute- just until fragrant.
• Stir in the chopped chicken & cooked rice until evenly incorporated. Reduce the heat to low, but don't forget to stir the mixture occasionally to prevent sticking while preparing the sauce.

To Make The Cheese Sauce

• In a large skillet, melt the butter over medium-medium high heat. Add the flour, whisking to evenly combine. Let the mixture bubble for roughly 30 seconds while you're whisking to cook off any flour taste. Season with salt & pepper.
• Whisk in the broth, a little at a time, until the mixture's thick, bubbly, and smooth.
• Once the mixture's thick and bubbling, whisk in 2 cups of the shredded cheddar. Whisk until the cheese is melted and the cheese sauce is smooth.
• Pour the cheese sauce into the chicken & veggie mixture, stirring until evenly incorporated.

To Assemble The Casserole

• Lightly spray a 9x13 inch casserole dish with non stick cooking spray
• Transfer the chicken & rice mixture to the dish, and use a spoon or spatula to evenly spread it out into the dish.
• Sprinkle the remaining 1 1/2 cups of shredded cheddar evenly out over top of the casserole.
• Bake at 350 degrees for 25-30 minutes, or until the casserole's hot & bubbly and the cheese is evenly melted over top.
• Remove the casserole from the oven, and let it rest for 5 minutes before scooping and serving.