1-First, preheat the oven to 350°F (175°C) and cut the chicken into bite-sized pieces, seasoning with salt and pepper.

2-Melt 2 tablespoons of butter in a large pot over medium heat, then add the chicken, diced onion, and celery, sautéing for 3 minutes until the chicken is halfway cooked.

3-Next, add the broccoli florets and olive oil, cooking for an additional 3-5 minutes until the chicken is fully done.

4-Remove the mixture from heat and stir in the cream of chicken soup, sour cream, milk, garlic powder, onion powder, mustard powder, and half of the shredded cheddar cheese.

5-Transfer everything to a lightly greased 9×13 inch casserole dish and top with the remaining cheese, then cover and bake for 20 minutes.

6-After that, increase the oven temperature to 400°F (200°C), mix the melted butter with crushed crackers, and sprinkle it evenly over the casserole.

7-Bake uncovered for another 8-10 minutes until the topping turns golden brown, then let it sit for 5 minutes before serving.