In a large pot, bring salted water to a boil and add the cubed potatoes. Cook for about 15 minutes, or until they are fork-tender. Drain and set aside.
In a large mixing bowl, combine the shredded chicken, ranch dressing, sour cream, 1 cup of cheddar cheese, ½ cup of chopped green onions, garlic powder, onion powder, salt, and pepper. Mix until well combined.
Gently fold in the cooked potatoes into the chicken mixture, being careful not to mash the potatoes.
Transfer the mixture into a greased 9x13 inch baking dish, spreading it out evenly.
In a small bowl, combine the panko breadcrumbs, remaining cheddar cheese, cooked bacon bits (if using), and olive oil. Mix until the breadcrumbs are evenly coated.
Spread the breadcrumb mixture evenly over the casserole.
Bake in the preheated oven for about 25-30 minutes, or until the top is golden and crispy.
Once done, remove from the oven and let it cool for a few minutes before serving.
Garnish with the remaining chopped green onions before serving.
Notes
Optional bacon bits can be omitted for a lighter dish.