To prepare shrimp, pinch off and discard the sharp point on the tail of each shrimp. Devein the shrimp by cutting along the back curve and removing the vein. To butterfly each shrimp, deepen the cut along the back slit, not cutting all the way through, to open up the shrimp. Flatten shrimp with the palm of your hand or the flat side of a cleaver. When all shrimp have been butterflied, sprinkle inside of shrimp lightly with salt and pepper.
Place cornstarch, egg whites and panko in three separate shallow bowls. Pick a shrimp up by the tail; dredge it in cornstarch, then dip in egg whites, and finally coat with panko, pressing shrimp into the panko to coat all sides evenly. Set aside on a plate. Repeat with remaining shrimp.
To deep-fry, heat oil in a wok to 325°F. Working in batches, add shrimp, one at a time, to oil in a single layer. Deep-fry until panko turns golden and a crust is formed. Turn shrimp over and fry for about 2 minutes total. Transfer to a paper towel-lined tray to drain.
To serve, arrange lettuce leaves on a platter. Place shrimp on top of leaves. Serve with Kikkoman Thai Style Chili Sauce in a small bowl for dipping.
Recipe courtesy of Chef Lawrence Chu