Cut the boneless, skinless chicken breasts into bite-sized pieces. Place the chicken pieces into a large mixing bowl and pour the buttermilk over them. Add 1 teaspoon of dried oregano, then cover and refrigerate for at least 30 minutes to tenderize and flavor the chicken.
In a shallow dish, combine the finely crushed corn flakes, all-purpose flour, remaining teaspoon of dried oregano, cayenne pepper, garlic powder, onion powder, sea salt, and black pepper. Mix thoroughly until well combined.
Pour enough oil into a frying pan or Dutch oven to cover the bottom by about an inch. Heat the oil over medium-high heat until it reaches 350°F (175°C). Use a meat thermometer to check the temperature.
Remove the marinated chicken from the refrigerator. Let excess buttermilk drip off, then coat each piece in the cornflake mixture, pressing the coating to ensure it sticks well.
Carefully place the coated chicken pieces into the hot oil, avoiding overcrowding. Fry for 4-5 minutes on each side or until golden brown and cooked through. Fry in batches if necessary.
Use a slotted spoon to remove the fried chicken and place on paper towel-lined plate to drain excess oil. Serve immediately with your favorite dipping sauces or store for later.