Preheat the oven to 350 degrees F (175 degrees C). Oil a baking dish.

Combine flour, garlic powder, onion powder, paprika, poultry seasoning, salt, and black pepper in a large resealable plastic bag. Add chicken and toss to coat well. Shake off excess breading.

Heat olive oil in a skillet over medium-high heat. Brown chicken on both sides, 5 to 10 minutes. Transfer to the prepared baking dish. Cook and stir potatoes in the same skillet until almost tender, 3 to 5 minutes. Transfer to the baking dish.

Add butter to the same skillet over medium-high heat. Saute mushrooms for 2 minutes. Add green onions and garlic and saute until garlic is browned, about 3 minutes. Add soup, broth, and sherry. Bring to a boil and cook until sauce thickens, about 5 minutes. Add spinach and cook until wilted, 2 to 3 minutes.

Pour sauce over chicken and potatoes in the baking dish. Top with mozzarella and Parmesan cheeses. Cover dish with aluminum foil.

Bake in the preheated oven for 20 minutes. Remove aluminum foil and bake for 20 minutes more.