First, line a rimmed baking sheet with parchment or foil. This will help catch any drips and make for easier cleanup later.
In a large shallow bowl, whisk together 3 cups of all-purpose flour, 1/8 teaspoon of cayenne pepper, 5 teaspoons of salt, and 1 teaspoon of freshly ground black pepper. This seasoned flour is the base for your crispy coating.
In a second shallow bowl, whisk 1 egg with 1 teaspoon of baking powder and 1/2 teaspoon of baking soda. Then, whisk in 1 cup of buttermilk until smooth. This mixture will be used to coat the steaks.
Pat the cube steaks dry with paper towels, and season both sides with salt and pepper. This step ensures that your meat is well-seasoned and delicious.
Working with one steak at a time, drop it into the seasoned flour, turning to coat completely. Shake off the excess flour, then dip the steak in the egg mixture, ensuring it’s well coated.
Return the steak to the flour mixture and dredge a second time, shaking off any excess flour. Place the coated steak on the lined baking sheet and repeat this process with the remaining steaks.
In a Dutch oven or large stock pot, heat 4 cups of vegetable oil to about 375 degrees Fahrenheit. You want enough oil to cover the bottom of the pan by about an inch.
Working in batches, fry the steaks until they are deep golden brown all over, turning frequently. This should take about 5 to 7 minutes for each steak.
Once fried, transfer the steaks to a plate and loosely tent them with aluminum foil to keep warm while you prepare the remaining steaks. Make sure not to discard the oil, as you'll need it for the gravy.
After frying all the steaks, reserve 2 tablespoons of oil from the pan and discard the rest. If desired, drain the oil through a fine-mesh sieve for a cleaner taste.
Reheat the reserved oil over medium-high heat until shimmering. Add the minced onion, minced garlic, and dried thyme. Cook until softened, which should take about 4 to 5 minutes.
Whisk in 3 tablespoons of all-purpose flour until cooked through, about 1 minute. This will create a roux for your gravy.
Next, gradually whisk in 1/2 cup of chicken broth, scraping up any brown bits from the bottom of the pan. This adds depth to your gravy.
Then, whisk in 2 cups of whole milk, pinch of cayenne pepper, and season with salt and pepper to taste. Bring to a simmer over medium-high heat and cook until slightly thickened, about 5 minutes. Be aware that the gravy will continue to thicken as it cools.
Serve the steaks warm, generously topped with gravy, alongside mashed potatoes if desired. Enjoy!