Preheat oven to 350ºF. Lightly spray a 9×13-inch baking dish with cooking spray. Set aside.: The warm oven creates an even heat that browns the stuffing while heating the filling. As the oven approaches 350ºF you will feel a gentle warmth and eventually see the faint glow of the heating element if your oven exposes that. Preparing the baking dish with a light coat of cooking spray prevents sticking and helps the edges release cleanly after baking. One thing I always check is that the oven rack is centered, so the casserole bakes evenly and the top browns without burning. A common mistake is not preheating long enough, which can cause uneven cooking and a paler topping, so wait until the oven fully reaches temperature.
Remove skin from chicken. Pull the chicken meat from bones and discard bones. Chop chicken meat and spread in bottom of the prepared baking dish.: The shredded chicken forms the hearty foundation of the casserole and spreads into a uniform layer that supports the filling. As you shred, notice the aroma of roasted meat, a sign of flavor depth. Chopping into even pieces helps the casserole hold together and makes bites consistent. Be mindful to remove bones and excess skin, because stray bits can make the texture uneven or leave fatty pockets. If the meat is cold it can be harder to shred, so slightly warm chicken makes pulling easier, but do not leave it too hot to handle safely.
Prepare stuffing mix according to package directions. Set aside.: The boxed stuffing needs to be hydrated to the right level so it crisps instead of sogging down the top. When preparing, pay attention to the steam and the texture as it comes together, aiming for fluffy, separate pieces rather than a paste. Fluffing it with a fork after preparation helps maintain air and promotes a crunchy finish once baked. A frequent error is adding too much liquid from the package directions or letting it sit too long and become compacted, so prepare it shortly before assembling the casserole for best results.
Combine sour cream, cream cheese, cream of chicken soup, and broccoli. Spread over chicken.: As you mix these ingredients, the texture should become smooth and creamy, with the softened cream cheese dissolving into the sour cream and soup. The mixture smells rich and savory, with green flecks of broccoli visible throughout. Spreading this layer over the chicken seals in juices and ensures each bite has a balance of protein, creaminess, and vegetable. If the mixture seems too thick to spread, a quick stir or gentle warming can help; conversely, avoid thinning it with extra liquid, otherwise the casserole will be loose after baking. One mistake is not distributing the broccoli evenly, which leads to pockets without vegetable; distribute it so each scoop is balanced.
Top casserole evenly with prepared stuffing.: This final layer is the visual star and the source of crunch, so aim for an even blanket of stuffing across the surface. Press down lightly so the stuffing makes contact with the filling, which helps it brown and adhere. As it bakes the stuffing will develop toasted, nutty aromas and a golden color, signaling readiness. A common oversight is piling the stuffing too thick in spots, which can leave raw pockets or overly browned peaks; leveling the top ensures consistent texture and doneness.
Bake uncovered for 30 minutes.: During baking the kitchen fills with an inviting smell of herbs, roasted chicken , and warm dairy, while the stuffing crisps and the filling bubbles gently at the edges. Baking uncovered allows moisture to escape so the topping becomes crisp, and the broccoli softens to tender vibrant green. Watch for visual cues like a bubbling seam around the edge and a golden top; these indicate the casserole is done. Avoid underbaking, which leaves the center cold, and overbaking, which dries the filling and can make the stuffing too hard. If the top is browning too quickly, tent with foil for the remaining time but keep it uncovered long enough to crisp.