Peel turnips & carrots. Use melon scoop to cut turnips into large balls. Slice carrots 1/2" thick; then with paring knife, cut 4 evenly spaced notches into rim of each slice (don't cut into center core).
Carrots should look like little flowers. Parboil turnip & carrots in stock until barely tender. Remove from stock & plunge pieces into cold water; drain. Cut onions, asparagus & baby corn into 1 1/2" pieces.
Mince together fresh ginger root & Tientsin preserved vegetable. Insmall pot or beaker on medium heat, render pieces of chicken fat.
Stir-frying: Add peanut oil to hot wok. When it begins to smoke, briskly fry crab meat or shrimp for 1 minute. Add asparagus, baby corn, mushrooms & water chestnuts, stir-frying until they are hot.
Add ginger mixture, then onions. Stir-fry another 30 seconds. Add 1/2 stock, salt & sugar; bring to boil. Add turnips & carrots. Cover & reduce heat; simmer for 5 minutes.
Uncover, push ingredients out of liquid, & dribble in cornstarch paste to thicken slightly. Stir liquid to prevent lumping while it thickens to a thick soup. Recombine, then mix in chicken oil. Remove to serving platter.