Place chicken breasts between plastic wrap and gently pound to 1/2-inch thickness. Season both sides with salt and pepper, letting the chicken rest while you prepare your coating station.

In a shallow dish, whisk together flour, garlic powder, onion powder, paprika, salt, pepper, and cayenne. In another dish, beat eggs with buttermilk until smooth.

Dredge each piece first in the seasoned flour, shaking off excess. Next, dip into the egg mixture, allowing any drips to fall back into the bowl. Finally, press firmly into the flour mixture again, ensuring complete coverage.

Pour oil to a depth of 1/2 inch in a large cast-iron skillet or heavy pan. Heat to 350°F, or test with a pinch of flour – it should sizzle immediately.

Carefully place coated chicken in hot oil, avoiding overcrowding. Cook 4-5 minutes per side until golden brown and internal temperature reaches 165°F. Transfer to a wire rack over paper towels.

Pour off all but 3 tablespoons of oil from the pan, keeping those flavorful brown bits. Whisk in reserved flour mixture and cook 1 minute. Gradually add milk, whisking constantly until smooth and thickened, about 3-4 minutes. Season with salt and pepper.