In a large skillet or Dutch oven, heat oil over medium-high heat. Pat chicken breasts dry with a paper towel, sprinkle with 1 teaspoon Kosher salt, 1/2 teaspoon black pepper, 1/2 teaspoon garlic powder, and 1/4 teaspoon onion powder. Rub to adhere and set aside. Have ready a large rimmed baking sheet, lined with paper towels and a cooling rack fitted atop.
Set up dredging stations using three rimmed dishes or trays, and placing them side-by-side. Add 1 cup of flour to the first tray. Whisk together milk, egg, and hot sauce and add to the second tray. Mix together 1 cup of flour, 1 teaspoon salt, 1 teaspoon dry mustard, 1/2 teaspoon paprika and 1/2 teaspoon black pepper in the third tray.
Dredge the chicken in the plain flour, then the egg mixture and then in the seasoned flour. Transfer back to the egg mixture and dredge in the seasoned flour once more.
Fry in the oil for 3-4 minutes on the first side, flip and fry 2-3 minutes more, or until the chicken is golden brown and is properly cooked through. Take care not to overcrowd the skillet. Set aside to cool on the rack and repeat with remaining cutlets.
Assemble the sandwiches with desired toppings, serve and enjoy.