Pound pork chops to 1/4-inch thickness; season with salt and pepper. Set aside.

Place 1/2 cup flour in a dish, beat egg in another, and stir together Panko bread crumbs and garlic powder in a third dish. Coat chops with flour, shaking off excess. Dip in egg coating on both sides; allowing excess to drip back into the bowl. Dredge in the Panko mixture.

Heat 1 1/2 tablespoons oil in a large skillet over medium heat. Add 2 pork cutlets and cook until browned on outside and cooked through, about 4 minutes on each side. Transfer to a plate; heat remaining oil in skillet and cook remaining cutlets.

Wipe skillet clean with paper towels. Melt butter in skillet over medium heat. Add mushrooms and saute until mushrooms are softened and they release liquid, about 5 minutes. Sprinkle flour and 1/2 teaspoon salt over mushrooms; cook 1 minute, stirring constantly. Stir in milk and broth; bring to a simmer, stirring constantly. Simmer until mixture thickens, about 3 minutes. Season with salt and pepper. Spoon over cutlets to serve.