Pound each chicken breast to an even thickness of about 1/2 inch using a meat mallet or rolling pin.

Arrange three shallow bowls on a work surface and fill one with flour, one with beaten eggs, and one with panko mixed with garlic powder, paprika, cayenne, salt, and black pepper.

Dredge each chicken breast in the flour, shaking off excess.

Dip the floured chicken into the beaten eggs, allowing excess to drip back into the bowl.

Press the egg-coated chicken into the panko mixture until fully covered on both sides.

Heat vegetable oil in a large skillet over medium-high heat for about 2 minutes until shimmering.

Pan-fry the chicken breasts for 5 to 6 minutes on each side, or until golden brown and the internal temperature reaches 165°F on a meat thermometer.

Transfer the cooked chicken to a paper towel-lined plate to drain and rest for 2 minutes. Meanwhile, spread mayonnaise on brioche buns and toast in the same skillet for 1 minute per side until golden.

Assemble each sandwich by layering chicken, lettuce, tomato slices, and a pickle on the bottom bun, then topping with the other bun half and serving immediately.