Preheat oven to 200°. Place a wire rack on a rimmed baking sheet; spray rack with cooking spray.
In a small bowl, whisk together Italian seasoning, garlic powder, salt, and pepper. In a medium bowl, combine beef, vinegar, and 2 tablespoons seasoning mixture. Divide mixture into 6 portions; shape each portion into a ½-inch-thick patty.
In a shallow dish, whisk together 1¼ cups flour and baking powder. In another shallow dish, combine buttermilk and hot sauce. Working in batches, dredge patties in flour mixture, shaking of excess. Dip in buttermilk mixture, letting excess drip off. Dredge again in flour mixture, gently pressing to adhere. Place on prepared rack.
In a large cast-iron skillet, pour oil to a depth of 1 inch. Heat over medium heat until a deep-fry thermometer registers 350°.
Working in batches, fry, turning occasionally, until golden brown, 5 to 6 minutes. Remove patties using a slotted spoon, and let drain on paper towels. Transfer steaks to a clean wire rack or baking sheet, and place in oven to keep warm. Reserve ¼ cup frying oil.
In a 10-inch cast-iron skillet, heat reserved frying oil over medium heat. Whisk in remaining ¼ cup flour and remaining seasoning mixture. Cook, whisking constantly, until flour is fully combined and mixture begins to bubble, about 2 minutes. Slowly whisk in milk. Cook, whisking constantly, until thickened and bubbly, about 5 minutes. Season with salt to taste. Serve gravy with patties. Garnish with pepper and green onion, if desired.
Recipe by Southern Cast Iron at https://southerncastiron.com/chicken-fried-hamburger-steak-gravy/