Prep. Place a wire-rack on top of a baking sheet. Set aside. Whisk together flour and Stone House Seasoning in a shallow bowl. Set aside. Whisk together buttermilk, hot sauce (if using), and egg in a second shallow bowl. Set aside.
Dredge cube steak. Pat cube steak dry with paper towels. Dredge the cube steak in the flour mixture, shaking off any excess flour. Then dip into the buttermilk mixture and back into the flour mixture. Place onto the wire-rack-lined baking sheet for 5 minutes to rest.
Preheat oven to 250º F.
Brown cube steaks. Add oil to a medium cast iron skillet set over medium-high heat. Once the oil begins to shimmer and sizzles when a bit of flour is sprinkled into the oil, it is ready to brown your cube steaks. Add two pieces of breaded cube steak to the skillet and cook 3 to 5 minutes. Carefully turn the cube steak over to cook the other side for 3 to 5 minutes. Remove from the skillet and return to the wire-rack-lined baking sheet. Repeat with the remaining breaded cube steak until all has been browned.
Hold warm. Place the cooked cube steaks into oven to keep warm while preparing the gravy.
Make the Gravy:
Pour off all but about 1/4 cup of the drippings from the skillet into a heat proof container. Return the skillet to the stove over medium heat. Once the drippings have heated throughout, sprinkle in the flour. Whisk the flour into the hot drippings and cook until browned throughout. Slowly pour in the milk, whisking the entire time. Add the salt and pepper and continue to whisk and cook until the gravy is smooth and creamy, about 7 to 10 minutes. Add more milk if the consistency becomes too thick. Remove from the heat and serve over the cube steak and mashed potatoes.