Pak Boong Tom Yum
“Water spinach (morning glory) in a tom-yum-style sour-spicy clear broth — minimal ingredients, bracing flavour, a Central Thai family-table soup.”
Where it comes from
Pak boong tom yum is a Central Thai household soup, not a restaurant tom yum. Where the famous tom yum kung uses shrimp and chile paste, this version is a vegetable-only weeknight read of the same template — the same lemongrass-galangal-lime aromatic backbone, but with morning glory as the body. The dish belongs to the Thai family of khaeng som and tom yum-style clear soups that cooks make from whatever vegetable came home from market that day.
On the plate
Clear broth with green confetti — water spinach stems hollow and crunchy like nature's straws, leaves silky. The aromatics hit first (lemongrass, galangal, kaffir), then the lime sour, then a chile heat that walks up the back of the throat slowly. No coconut, no chile paste, no cream — every flavour is broth-and-aromatic transparent. If the spinach is dark olive instead of bright green, it overcooked; if the lime tastes acrid, it was added in the boil.
How it works
Two rules separate this from a generic green-vegetable soup. One: lime juice goes in OFF the heat — limonin in lime peel becomes bitter above 70°C, and the sour-aroma volatiles flash off in a boil. Two: water spinach has hollow stems that fill with broth on first contact and lose crunch within 2 minutes — so the cook plans to eat it within 5 minutes of plating, not later. This is not a soup that holds.
Central Thai weeknight soup, not the restaurant tom yum kung. Same lemongrass-galangal-kaffir backbone, water spinach as the body, no chile paste, no coconut. Lime juice goes in off the heat — limonin turns bitter above 70°C.
Variations
Tom yum pak boong (vegetable-only); tom yum khai (with egg dropped in); tom yum hed (mushroom version using straw and oyster); Lao-Isaan kaeng som pak boong runs sourer with tamarind instead of lime.
On the Palate
Ingredients
Serves 4
How it's made
5 steps · Show ↓12 min active · 3 min waiting
How it's made
5 steps · Show ↓- 16 min
Bring 1.2L water or light pork stock to a simmer. Add 2 stalks of bruised lemongrass cut in 4cm sections, 5 slices fresh galangal (kha), 4 torn kaffir lime leaves. Simmer 5 minutes — broth should smell sharply citrus.
- 24 min
Wash 400g water spinach (pak boong); discard tough lower stems, cut the rest into 6cm lengths. Crush 4 garlic cloves and 6 bird's eye chiles together with the side of a knife — don't mince.
- 31 min
Drop crushed garlic and chile into the simmering broth. Add 2 tbsp nam pla (fish sauce), 1 tsp sugar. Simmer 1 minute.
Watch outEnsure the broth is simmering gently; boiling can cause the flavors to become harsh.
- 42 min
Add the water spinach. Push down with the back of a spoon to submerge. Cook exactly 60-90 seconds — stems still snap, leaves just collapse. Off heat immediately.
Watch outDo not overcook the water spinach; it should remain vibrant and crisp.
- 51 min
Squeeze in the juice of 1.5 limes off the heat (boiling lime turns it bitter). Tear in a small handful of culantro or sawtooth coriander. Ladle into bowls so each gets stems, leaves, and a fierce piece of chile. Serve with steamed rice.
Watch outAdd lime juice only after removing from heat to prevent bitterness.
