Preheat the oven to 350°F (175°C). Grease a 9×13 inch baking dish.

Cook the chicken in a skillet over medium heat until golden brown, about 7-10 minutes.

Sauté mushrooms and spinach in the skillet, cooking for about 5 minutes until the mushrooms are tender and the spinach is wilted.

Mix the creamy base in a large bowl by combining the cooked chicken mixture with softened cream cheese, garlic powder, onion powder, salt, and pepper.

Spread the chicken mixture evenly into the prepared baking dish.

Top the casserole with shredded cheese and panko breadcrumbs.

Bake in the preheated oven for 30-35 minutes until bubbly and golden brown.