I like to serve this over rice.
Adding the canned chow mein noodles and cashews before baking causes them to burn and lose their essential crunch, so sprinkle those toppings over the casserole during the final five minutes in the oven or right after baking. Fat separation happens when cream of mushroom soup bases are subjected to excessive heat, which is why keeping the oven set strictly at 350 degrees Fahrenheit prevents the sauce from breaking or curdling. Sautéing the diced onions and celery in butter until fully translucent removes excess moisture that would otherwise water down the chicken broth and soy sauce emulsion.
Preparing this dish in advance requires assembling the unbaked chicken, mushroom, and soup mixture in a two-quart baking dish, covering it tightly, and refrigerating it for up to 24 hours before cooking. Freezing the unbaked casserole works successfully if the dairy-heavy sauce is wrapped in heavy-duty aluminum foil for up to one month, though thawing it completely in the refrigerator overnight is mandatory to ensure even internal heating. Reheating leftovers should be done gently at 325 degrees Fahrenheit until steaming throughout, protecting the top layer from scorching by tenting it loosely with foil.
Scaling this recipe up or down requires careful adjustment of the baking dish size to maintain a consistent two-inch depth, ensuring the interior heats through without drying out the edges. Doubling the ingredients demands upgrading to a 9x13-inch pan and extending the initial oven time by roughly ten minutes, while checking for a central bubbling cue to confirm safe serving temperatures. Using a broader pan also prevents the cubed chicken from overcrowding, which allows the heat to penetrate every layer uniformly.
Cube the cooked chicken uniformly into half-inch pieces so that each spoonful contains an equal proportion of meat, vegetables, and sauce. Slicing the fresh mushrooms to an even thickness ensures they release their moisture evenly into the butter during the initial stovetop reduction. Stirring the soup and broth mixture thoroughly before adding the solids eliminates pockets of pure sodium or isolated seasoning clumps.