Drop the shelled walnuts into boiling water for 1-2 minutes.
Drain, peel, dry thoroughly and set aside.
Cut the duck leg diagonally into slices half as large again as the half walnuts.
Dice the cucumber, thinly slice the bamboo shoots and slice the chestnuts more thickly.
Set each aside separately.
Heat the oil in a frying-pan.
Lightly brown the walnuts in it then lift them out.
Add the onion and cook for 1 minute, then add the duck and fry for 3 minutes at high heat, tossing and turning the pieces about.
Add the cucumber, bamboo shoots and chestnuts in that order and cook for 2 minutes.
Add the stock, seasonings soy sauce and cook for 1 minute.
Add the walnuts and heat through.
Blend the cornflour with the water, stir it in and cook for 1 1/2 minutes.