Cut cube steak into strips. Place meat in glass bowl and cover with buttermilk. Place in fridge and let sit for up to 12 hours. Just before removing meat from buttermilk, add beaten egg to buttermilk mixture.
In a shallow dish, such as a pie plate, combine flour, salt, pepper, and seasonings.
Working with one piece at a time, remove piece of meat from buttermilk and dredge in flour mixture. Flip to coat each side. Press flour into it. Pick up piece and shake off excess flour. Continue working until all pieces are covered.
Heat frying oil in deep skillet or dutch oven to ~325°F-350℉. Working in batches, carefully place breaded steak in the hot oil. Fry for 3-5 minutes and then flip over and continue to fry until fully cooked through and internal temperature of 160°F is reached.
Remove and place on baking rack over baking sheet. Can keep warm in oven if necessary.
To make gravy:
Take 2 Tbsp. of oil and drippings from pan and place in saucepan over medium heat. Whisk in 2 Tbsp. flour and cook for 1-2 minutes. Reduce heat and whisk in milk. Whisking frequently, cook over low until gravy thickens. Season with salt and pepper to taste.