Add all listed ingredients to a medium bowl. Season with ½ teaspoon kosher salt & ground black pepper as desired. Mix to combine well; if needed, adjust seasonings to taste. Cover & chill until serving, or store in an airtight container in the refrigerator for up to 1 week.
Pour the oil into a medium skillet. The amount of oil needed depends on the size of your skillet & the thickness of the fish – use just enough such that the oil comes halfway up the sides of your thickest piece of fish. Preheat over medium-high heat. The oil is ready once it sizzles when you sprinkle a breadcrumb or two into the skillet.
Cut the cod fillet into 8 uniform pieces, each about 2-3 inches wide. Using paper towel, pat the fish as dry as possible, then season with seasoned salt, garlic powder, & white pepper.
Create a dredging station by placing the rice flour, beaten eggs, & panko breadcrumbs in separate bowls. Season each bowl with S&P. Working one by one, give each portion of cod a light dusting of flour, followed by a light coating of egg. Place the cod into the panko breadcrumbs, pressing to adhere & coat the fish. Shake off any excess breading & set aside. Repeat with the remaining cod.
Once the oil is hot, use tongs to transfer prepared cod into the skillet. Work in batches. Cook 1-3 minutes per side, or until panko coating is golden brown & the cod is cooked to your liking. Once both sides are golden brown, transfer the fried fish to a paper towel-lined plate to drain excess oil. Season with a good pinch of salt while the fish is still warm. Repeat with the remaining breaded cod.