In a dish, mix 1 1/2 cups of the milk with the eggs.
In a second dish, mix 2 cups of the flour, 2 teaspoons of the seasoned salt, the black pepper, the paprika, and the cayenne together.
In a third dish, add the cube steak.
Place 1 clean plate next to the 3 dishes to receive the breaded meat.
Working with 1 piece of the meat at a time, sprinkle each piece with the salt and the pepper.
Place the seasoned meat in the flour mixture and turn to coat.
Place the meat in the milk mixture and turn to coat.
Place the meat back in the flour mixture and turn to coat a second time.
Place the breaded meat on the clean plate and repeat with the remaining meat.
In a large skillet over medium heat, heat the oil.
Add the butter to the oil.
Drop in a few sprinkles of the flour to make sure it's sufficiently hot. When the butter sizzles immediately, that's when it is ready. The butter should not brown right away, and if it does, the skillet is too hot.
Cook the meat in the skillet, 3 pieces at a time, until the edges start to look golden-brown and the internal temperature reads 145 degrees F, about 2 minutes for each side.
Transfer the cooked meat to a paper towel-lined plate and keep it warm by covering it lightly with another plate or a sheet of foil.
Repeat the cooking process until all the meat is cooked.
Pour the grease from the skillet into a heat-proof bowl.
Without wiping the skillet, return it to the stove-top over medium-low heat.
Add 1/4 cup of the grease back into the skillet and allow it to heat up.
Sprinkle the remaining 1/3 cup of flour evenly over the hot grease and whisk until a golden-brown paste has formed.
Add more of the flour to the mixture if the mixture looks overly greasy; add more of the grease if it becomes too clumpy or pasty.
Cook the grease mixture until the roux reaches a deep golden-brown color, about 2-4 minutes.
Pour the remaining milk into the grease mixture, whisking constantly.
Add the remaining seasoned salt and the black pepper to the gravy mixture and cook, whisking constantly, until the gravy is smooth and thick, about 5-10 minutes.
If the gravy becomes overly thick, add more of the milk. Be sure to taste the gravy to ensure it is seasoned as desired.
Plate the meat next to the mashed potatoes and pour the gravy over both.
Serve.