Preheat the oven to 350 degrees Fahrenheit. Grease a 13 x 9-inch casserole dish with nonstick cooking spray.
Steam or blanch 3 cups broccoli florets until tender and crisp. Layer the broccoli evenly on the bottom of the casserole dish.
Layer 4 cups cooked, diced, or shredded chicken evenly over the broccoli.
In a bowl, combine 1 (10.5-ounce) can cream of chicken soup, ¾ cup sour cream, ½ cup milk, 1 tablespoon lemon juice, ½ teaspoon garlic powder, ½ teaspoon onion powder, salt and pepper, and 2 cups shredded cheddar cheese.
Pour the sauce over the chicken and broccoli, spreading out evenly.
In a bowl, mix 1 cup crushed Ritz crackers and 2 tablespoons melted butter. Sprinkle over the top of the casserole. Bake for 40-45 minutes, until hot and bubbly, and the cracker topping is golden brown.
Notes
Storage & Reheating Instructions
Fridge: Once cooled, store in an airtight container in the fridge for 3-5 days.
Reheat: Microwave or oven at 350ºF until warmed through.
Freezer: Assemble the unbaked casserole, then wrap it tightly, without the crumb topping. Freeze for up to 3 months. Thaw in the fridge overnight, add topping, and bake.
Make Ahead- Assemble the casserole ahead of time, without the crumb topping. wrap tightly, and store in the fridge up to 2 days. Add topping when ready to bake.