Soak the cutlets in buttermilk for 30 minutes in the refrigerator, then let the excess drip away.
Mix 1 1/4 cups flour with 1 teaspoon salt, paprika and pepper and coat each cutlet once, pressing lightly.
Heat 1/2 inch oil in a wide skillet to 340°F and fry the cutlets in two batches for 3 to 4 minutes per side until 165°F.
Drain the chicken on a rack, pour off the oil and return 3 tablespoons of it to the skillet.
Cook the sliced onion with the remaining 1/2 teaspoon salt for 8 minutes until soft and well browned.
Sprinkle in the remaining 1/4 cup flour and cook for 1 minute, then gradually stir in the broth and Worcestershire.
Simmer for 5 minutes until the gravy is glossy and spoonable, then plate it around the rested chicken.