Mix 1 cup flour, 1/2-tsp. salt and 1/2-tsp. pepper in a shallow dish. In a second dish, mix the buttermilk, egg, mustard, and bouillon with a whisk. Add 1/2-tsp. salt and 1/2-tsp. pepper.
Dip each steak in the seasoned flour and shake off excess. Dip the floured steaks into the buttermilk mixture and again into the flour. Shake off excess.
Heat 2-3 inches of vegetable oil in a frying pan over medium high heat to 360°F Use a thermometer to check the temperature of the oil.
Carefully drop the steak into the hot oil and cook for 3-5 minutes on each side until golden brown.
Drain on clean paper towels and keep warm.
Pour all but 4 tablespoons of oil from skillet. Over medium heat, whisk in 4 tablespoons flour. Slowly add 2-1/2 cups of milk, stirring continuously. Continue to stir until gravy thickens and just begins to boil. Season with salt and black pepper to taste.