Place the beef steaks on a cutting board. Using a meat mallet, pound each steak vigorously until they're well-tenderized and about 1/8-inch thick. Season both sides with salt and pepper.

In a large bowl, combine 3 cups of flour with 3 tablespoons of the seasoning salt. In a separate bowl, mix the buttermilk with the remaining 1 tablespoon of seasoning salt.

Dredge each tenderized steak in the flour mixture, then dip into the seasoned buttermilk, letting excess drip off. Return to the flour for a second coating, pressing gently to help the flour adhere. Place on a rack while preparing to fry.

Heat vegetable oil in a large, heavy skillet to about 1/2-inch deep and 350°F (hot enough that a pinch of flour sizzles immediately when dropped in).

Carefully add the steaks to the hot oil and fry for 3-4 minutes per side until golden brown and crispy. Remove and drain on paper towels.

Dredge the oysters in the remaining flour mixture, then dip in buttermilk, and coat again with flour. Fry in the same oil for about 2 minutes until golden and crisp. Remove and drain.

Pour off most of the oil, leaving about 2 tablespoons in the skillet. Add the chopped onion and green onions, cooking until softened, about 2-3 minutes.

Sprinkle in 2 tablespoons of flour, stirring constantly to make a roux. Cook for 1-2 minutes until light golden.

Slowly whisk in the milk, then season with 1 teaspoon salt, 1 teaspoon black pepper, and 1/2 teaspoon seasoning salt. Simmer, stirring frequently, until thickened to gravy consistency, about 5 minutes.

Serve the chicken fried steak topped with fried oysters and cream gravy poured over everything.