Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine the cooked, shredded chicken, cream of chicken soup, sour cream, mayonnaise, garlic powder, onion powder, salt, and pepper. Mix until well combined.

Stir in 1 cup of shredded cheddar cheese and half of the crushed Ritz crackers into the chicken mixture.

Transfer the chicken mixture into a greased 9x13 inch baking dish, spreading it evenly.

In a separate bowl, combine the remaining crushed Ritz crackers, melted butter, and the remaining 1 cup of shredded cheddar cheese. Mix well.

Sprinkle the cracker and cheese mixture evenly over the chicken mixture in the baking dish.

If using, sprinkle chopped green onions over the top.

Bake in the preheated oven for 30-35 minutes, or until the casserole is bubbly and the top is golden brown.

Remove from the oven and let it cool for a few minutes before serving.