Preheat your oven to 375 F and move the rack to the middle position.: Warmth should fill your kitchen and you may notice a faint toasty scent as the oven reaches temperature, which helps the top brown evenly. This middle placement ensures balanced heat circulation so the center cooks at the same pace as the edges. A common mistake is placing the dish too low which can burn the bottom before the top sets, so double check the rack position before sliding the casserole in.
Add the cream of chicken soup and chicken broth to a bowl and stir together until combined.: You will see the condensed soup loosen and the liquid become silky, stirring away lumps so the sauce is smooth. The aroma will be lightly savory and slightly salty, signaling a good flavor base. If you skip stirring well, pockets of concentrated soup can create uneven texture in the finished dish, so whisk until smooth.
Grease a 9×13 casserole dish (I use Pam cooking spray).: Greasing prevents sticking and helps the edges brown gently, producing a clean slice when serving. You might notice a slight sheen on the dish once it is prepped, which is what you want. Using too little oil can cause the casserole to cling to the dish, so ensure full coverage, especially along the corners.
To the casserole dish, add the rice, chicken, veggies, garlic powder, onion powder, Italian seasoning, pepper, scallions, and one cup of the cheddar.: As you layer these, the rice looks dry but will absorb the sauce, the shredded chicken adds visible strands of protein, and the frozen vegetables bring flecks of color. The spices will distribute aroma and subtle flavor notes, and the first cup of grated cheddar will begin to meld during baking. A typical error is uneven mixing at this stage, which can leave pockets of dry rice , so rake a fork through the mixture to distribute everything evenly.
Pour the soup/broth mixture into the casserole dish, toss until everything is coated thoroughly, and smooth in an even layer.: You will feel the mixture become glossy and slightly thick as the sauce clings to the rice and chicken . The visual cue is a uniform, moist surface with no dry pockets, and the scent will be savory and inviting. If you pour unevenly and fail to toss well, some areas will remain too dry after baking, so use a large spoon to fold gently until every grain looks hydrated.
Cover the casserole dish tightly with foil or the lid it came with (important so the rice cooks properly!). Bake for 45 minutes.: Covered baking traps steam so the instant rice softens and becomes creamy while the flavors meld. You may hear a gentle bubbling as the sauce simmers beneath the foil, and if you lift the cover slightly you will feel warm steam escape. A common slip is to use loose foil which allows steam to escape, drying out the casserole, so press the foil edges to seal tightly.
Take the casserole dish out of the oven, carefully remove the foil, and top with the remaining cheese. Return to the oven and bake uncovered for another 10-15 minutes or until the cheese is nicely melted and the rice is soft and creamy.: When you pull back the foil, the scent becomes richer and you may see the sauce gently bubbling. Adding the top layer of cheddar creates a golden, bubbling crust as it melts and browns; visually look for an even melt and light browning. Leaving it in too long can overbake the top and dry the interior, so watch for the cheese to be melted through and slightly golden, and test the center for creamy rice before removing.