Shell and devein shrimp. Cut onion in half; slice thinly.
Blend cornstarch, water, sugar and pepper to a paste. Set aside.
Heat oil. Add salt, then shrimp, and stir-fry 1 minute. Sprinkle shrimp with sherry (off flame); stir-fry until pinkish (about 1 minute more). Remove and set aside.
Using a clean pan, add curry powder; stir 1/2 minute over low heat. Add onion and stir-fry until curry smells pungent (about 1 minute more). Return shrimp. Stir in stock and heat quickly. Then cook, stirring, until onon softens. Stir in cornstarch paste to thicken. Serve at once over rice, if preferred.