1.Hold squid firmly with one hand. With the other hand, hold head and pull gently. Head and inside of body of squid will come away in one compact piece. Remove bone which will be found at open end of squid; it looks like a long thin piece of plastic.
2.Clean squid under cold running water, then rub off the outer skin. (Some large food stores have squid available, already cleaned, ready for cooking).
3.Cut squid lengthwise down centre. Spread squid out flat with the inside facing upwards. With sharp knife make shallow cuts across squid in diamond shape; this helps tenderise squid and make it curl attractively when cooking.
4.Heat oil in pan or wok, add squid, cook until it curls, remove from pan, drain on absorbent paper. Add onions, celery, broccoli and ginger to pan, saute 3 minutes.
5.Blend cornflour with a little of the water until smooth, add remaining water, dry sherry, crumbled stock cubes, oyster sauce, soy sauce, sesame oil, sugar and salt; mix well.
6.Add to pan, stir until sauce boils. Return squid to pan, cook until heated through. Put on serving dish, top with shallots.