Preheat your oven to 375°F and lightly spray an 11×7-inch baking dish with cooking spray.
In a large bowl, combine the diced chicken, defrosted broccoli, condensed cheddar cheese soup, condensed cream of chicken soup, mayonnaise, milk, and half of the shredded cheddar cheese. Mix everything until well-incorporated, then transfer to your prepared baking dish.
Sprinkle the remaining shredded cheddar cheese evenly over the top.
In a zippered plastic bag, combine the crushed Ritz crackers with melted butter. Toss until the crumbs are evenly coated, then sprinkle over the casserole.
Bake for 30–35 minutes, or until the casserole is bubbly and the cracker topping is golden brown.
Garnish with dried parsley, if desired, and serve immediately.
