- Beat egg and 1 Tbsp. water together in medium bowl.
- Cut chicken across the grain into 1/2-inch thick slices.
- Dredge chicken in flour, shaking off excess. Dip chicken into egg mixture and then coat both sides with panko, pressing panko onto chicken.
- Pour enough oil into large, heavy pot to measure 2 inches deep; heat oil over medium heat to 350°F.
- Working in batches, deep-fry chicken in hot oil until cooked through, about 2 minutes, turning pieces over once. Remove chicken and drain on paper towels.
- Serve chicken with sriracha mayo, if desired.