For dashi, refrigerate kombu in 1.5 litres cold water in a jug overnight to steep.

Preheat oven to 200C and roast chicken wings and carcass in a roasting pan until browned (1-1¼ hours).

Transfer to a large saucepan, add kombu water (discard kombu), celery, onion, leek and 1.5 litres cold water, bring to the boil, then simmer over low heat until stock is well flavoured (4 hours).

Remove from heat, add katsuobushi and leave to steep for 1 hour.

Strain, add soy sauce, Shaoxing wine and 1-2 tsp finely crushed white pepper to taste.

Makes about 1.5 litres. Dashi can be made a few days in advance and kept refrigerated.

For wontons, mix ingredients except wrappers in a bowl to combine well.

To check seasoning, boil a small ball of filling, then taste and adjust.

Refrigerate filling to chill (1 hour).

Lay out 4 wrappers and place a teaspoonful of filling in the centre of each.

Brush edges lightly with water, bring corners together and pinch wrapper over filling to seal, pushing out any air bubbles.

Place on a tray and cover with a tea towel while you make remaining wontons.

They can be made 2 hours ahead and kept covered and refrigerated.

Bring dashi to the boil, add wontons in batches and simmer until they float (4-5 minutes).

Transfer to warm bowls with a slotted spoon, then add Chinese broccoli to dashi and cook until wilted (2 minutes).

Divide broccoli among bowls, ladle in dashi, garnish with fried shallots, sliced spring onion and a drizzle of sesame oil, and serve.