Pound chicken breasts, one at a time, in a resealable plastic bag until about 1/2-inch thick.

Lightly beat egg in a shallow bowl. Combine panko crumbs, garlic powder, onion powder, salt, and pepper in a separate shallow bowl.

Dip chicken breasts in egg until coated, then dip in panko mixture, pressing chicken into the crumbs until fully coated. Arrange in a single layer on a plate.

Heat oil in a large skillet over medium-high heat. Add chicken and cook until golden brown and cooked through, about 2 to 3 minutes per side.