Heat & Cooking Methods

Double-Boiling / Dun

Also: 炖, dùn, sealed steaming, Cantonese double-boil, zheng dun

A Cantonese technique in which a sealed inner vessel sits inside a larger pot of boiling water, cooking delicate soups, tonics, and desserts by entirely indirect, vapor-transmitted heat.

/DWUN/Cantonese; 炖 (dùn) denotes a slow, sealed, steamed-infusion method distinct from the Mandarin use of 炖 for braising; the character compounds 火 (fire) with 屯 (to store/accumulate), capturing the idea of accumulated, trapped heat

Definition

Double-boiling (炖, dùn) is a two-vessel wet-heat method foundational to Cantonese restorative cooking. The food — typically a whole soup, tonic broth, or sweet dessert — is placed inside a ceramic or porcelain pot with a fitted lid. That inner vessel is set inside a larger pot of water, which is then brought to a boil and maintained at a steady simmer. The outer water never contacts the food; heat transfers solely through the ceramic wall via steam and conducted warmth from the water surrounding it. Because the inner pot is sealed with its own lid and the outer pot is usually covered as well, pressure stays minimal and the temperature at the food surface never exceeds approximately 95–98 °C — below a full rolling boil. This gentleness is the method's entire point. Collagen-rich ingredients (whole silkie chicken, pork ribs, snow fungus) release gelatin without emulsifying fat or clouding the broth. Volatile aromatics (chrysanthemum, goji berry, dried longan) are preserved rather than driven off. Egg-based desserts (steamed egg custard, snow pear with rock sugar) set to a trembling, smooth consistency that direct heat would curdle. Traditional Cantonese double-boil sessions run two to four hours, and some tonic soups for postpartum recovery or winter warming are held for six hours or more. The method is also used for melting chocolate and holding hollandaise in Western kitchens, though it is rarely described with the same systematic rigor the Cantonese tradition brings to it.

In use

“The papaya and snow fungus tonic had been double-boiling for three hours, the sealed crock drawing a faint constellation of condensation on the outer pot's lid — the soup inside clear, golden, and barely trembling.”

Related terms

Bain-marieSteamingIndirect heatCollagen extractionTonic soupSilkie chicken

References

1.The Wisdom of the Chinese Kitchen — Grace Young
2.Breath of a Wok — Grace Young & Alan Richardson
3.The Food of Cantonese: Classic Recipes from Canton Province — various
4.On Food and Cooking — Harold McGee

Confidence: high

Notes

Why the broth stays crystal clear

In a direct-heat braise or boil, turbulent convection agitates fat droplets and coagulated proteins into the liquid, producing cloudiness. The double-boil's near-still, sub-boil environment keeps fat globules intact and proteins settled, yielding the signature jewel-clear, deeply flavored broth Cantonese cooks prize.

Vessel tradition

Authentic dùn uses a 燉盅 (dùn zhōng), a lidded ceramic crock with a flared rim that rests inside the outer pot without touching the bottom. The unglazed base of many traditional crocks allows minimal moisture exchange with the steam below while preventing the crock from bouncing on a boiling surface.

Not the same as 紅燒 (hóng shāo) or slow braising

In Mandarin usage, 炖 often means a slow simmered braise (直接加热). The Cantonese double-boil is a distinct enclosed-vessel steam method. The distinction matters culinarily: the Cantonese dùn never browns the protein first, never reduces the liquid through evaporation, and produces a lighter body and different flavor profile than any form of direct-heat 炖.