In a bowl, whisk together the buttermilk and beaten egg until combined. Add salt, pepper, garlic powder, and paprika. Submerge the beef steak in the marinade and let it marinate for at least 15 minutes.

Set up three shallow dishes: in the first, combine all-purpose flour and cornstarch with seasonings. The second dish holds the buttermilk mixture, and the third is empty for the breaded steak.

After marinating, remove the steak from the buttermilk, coat it in the seasoned flour mixture, dip it back into the buttermilk, then dredge again in the flour mixture.

Heat about half an inch of vegetable oil and add butter in a large skillet over medium-high heat until it reaches 350°F.

Fry the breaded steak for 3-4 minutes per side until golden brown and cooked through. Adjust oil temperature as necessary.

Remove from the skillet and drain on a paper towel-lined plate. Serve hot.