Place thawed shrimp in a bowl and cover with buttermilk, soak for 30 minutes or more
Mix cornstarch, panko crumbs and baking soda in a shallow bowl.
Place cooking oil in a 2 quart sauce pan and heat oil to 375°
Remove 10 to 12 shrimp from the buttermilk, pat dry on paper towels, coat with cornstarch/panko mixture, place shrimp in a spider mesh basket and lower into hot oil. (You can also carefully lower the shrimp into the oil one at a time, fry and remove from the oil with a spider).
Fry for 2 minutes, or until the shrimp is medium browned.
Remove the shrimp and place on a cooling rack.
Repeat for the remaining shrimp.
Coat the shrimp with the sauce, serve on a bed of chopped lettuce, garnish with chopped green onion.