Sweet potato and ginger sweet soup

Ingredientsserves 4

Method

1. Peel the sweet potato and cut it into chunks the size of a mahjong tile; keep them in cold water so they do not darken. Cut too small or boiled too hard, the potato collapses into the water.
2. Wash the ginger but do not peel it; cut it in thick slices and smash each slice with the back of the cleaver. Ginger that is not smashed gives nothing.
3. Bring five cups of water (about 1.25 litres) and the ginger to the boil and let them simmer ten minutes, so the water tastes of ginger before the potato goes in. Ginger and potato in together makes a pot that tastes of raw ginger.
4. Drain the potato, add it, bring back to the boil, lid on, and simmer on medium-low twenty to twenty-five minutes until a chopstick goes in without resistance. If using dried longan and red dates, add them with the potato for a darker pot.
5. Add the slab sugar, let it dissolve, five minutes more, and taste; sweet potatoes vary, so the sugar goes up or down. Sugar last, as always, or the potato takes longer to soften.
6. Serve hot, a slice of the ginger in each bowl. On the night of the winter solstice this pot is the syrup the glutinous rice balls go into.

Take care

• None of the declared allergens. Peel the sweet potato; the skin of the purple kinds bleeds colour. The syrup comes off the stove boiling hot, so let a child's bowl cool a little first.

The story

The cheapest sweet soup there is, and the one Hong Kong ties to the winter solstice, when the mature ginger and the slab sugar are the point. It is also the pot a mum makes on a weeknight from whatever is in the vegetable drawer, which is why it never appears on a dessert-shop menu and every family has it.

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Lo Fo Tong is cultural food-heritage reference, not medical advice. If you are pregnant, unwell or on medication, talk to your doctor or registered practitioner before changing what is in the pot.