Tom Kha Hed (ต้มข่าเห็ด)

The Soup That Names Its Herb

ต้มข่าเห็ด reads like a recipe in three words: ต้ม (tom) is boiled, ข่า (kha) is galangal, เห็ด (hed) is mushroom. The galangal is the one ingredient you cannot swap — swap the herb and the soup loses its name — while the mushroom part is famously flexible. Thai cooks list whatever the market has: straw, oyster, king oyster, wood ear, enoki, shiitake, or all of them at once.

Unlike its famous sibling ต้มข่าไก่ (tom kha gai), the mushroom version barely appears on restaurant menus — it is overwhelmingly a home dish, and overwhelmingly a เจ (je) one. Almost every Thai recipe for it comes framed as festival food: the Pantip auntie posts hers during เทศกาลกินเจ, the nine-day vegetarian festival, and calls her two-mushroom pot ต้มข่าเห็ดสองเกลอ — "the two mates" — because it uses oyster and king oyster mushrooms. Wongnai's version swaps chicken for three mushrooms and sheets of โปรตีนเกษตร (textured soy protein), keeping the body of the soup without the meat. Kapook notes the same door both ways: tom kha takes chicken, pork, fish, prawns — or none of them, made เจ with mushrooms only.

The taste the Pantip cook describes is the target: salty first, sweet following, and only a whisper of sour from lime to cut the rich coconut — with the mushrooms giving a texture no chicken can, crisp and springy by turns. Her version is served over hot rice; the mushroom soup is both broth and topping.

The Recipe (je version, from Phol Food Mafia / พล ตัณฑเสถียร)

The two-mates pot (Pantip): 200 g oyster mushrooms, 200 g king oyster, 12 slices young galangal, 2 stalks lemongrass, 4 torn kaffir leaves, sawtooth coriander, 4 fresh chillies, ½ tbsp lime juice, 1 tsp salt, 1 tbsp je soy sauce, ½ tbsp je seasoning powder, 1 tbsp sugar, 250 ml coconut cream, 200 ml water — serves 3–4, eaten over rice. The three-mushroom pot (Wongnai): 2 soaked shiitake, 6 wood ear, a bunch of enoki, 2 sheets textured soy protein, 1½ cups water, ½ cup coconut milk, lemongrass, 5 kaffir leaves, half a head of galangal, seasoned with soy sauce, sugar and 3 tbsp tamarind. The straw-mushroom pot (Cookpad): 250 g straw mushrooms, half a cabbage, 250 g coconut milk, a cup of young galangal, palm sugar, soy and mushroom sauces — lime or tamarind to sour. The chicken reference (Kapook): the same soup built on chicken with fish sauce, lime going into the bowl off the stove.

The Method

1. The fried chilli. Soak the dried chillies until pliable, then fry them in the oil until crisp and dark red. Pound two of them to a coarse powder and keep the rest whole for the garnish. This is the soup's heat — and its finish.
2. The toasted herbs. Bruise the galangal, lemongrass and fresh chillies, then dry-toast them in the pan with the kaffir lime leaves until they smell. Phol's step, and it is what makes this pot deeper than a plain boil: the herbs give their aroma to the oil before the liquid ever arrives.
3. The liquid. Add the coconut water, coconut milk, sugar, salt and tamarind paste. The coconut water keeps the richness in check — the soup should coat, not weigh.
4. The mushrooms. Bring to the boil, drop the heat, and add the oyster, king oyster and wood ear mushrooms with the coconut shoot. Simmer five minutes, no more — mushrooms are quick, and the soup should taste fresh.
5. The finish. Add the enoki, the lime juice and the pounded chilli, bring it back to the boil once and take it straight off. The enoki stays silky, the lime stays bright. Garnish with the remaining fried chillies and serve over rice or as a bowl of its own.

Where Thai Sources Disagree

How Western Versions Get It Wrong

• Ginger instead of galangal. The soup is named after ข่า, and the two are not interchangeable — ginger is hot and lemony, galangal is piney and peppery. A ginger "tom kha" is a different soup wearing the name.
• Curry paste, stock cubes, garlic. Tom kha is herbs in coconut milk — there is no paste, no stock, and Thai sources add no garlic. Western recipes that start with a red-curry-paste base are making something closer to a curry than a tom kha.
• Boiling the coconut hard. The Thai rule, from Veggie Kitchen in plain words, is low heat so the coconut milk does not split (อย่าให้แตกมัน). A hard boil breaks the milk into oil and scum, and the silky texture the dish is known for is gone.
• Cooking the lime. Lime juice that boils turns bitter and the brightness dies. Every Thai source puts it in last — off the heat, or into the bowl.
• Dairy. Cream, crème fraîche, milk — none of it belongs. The richness is coconut milk, full stop, and the sour is lime or tamarind, not yoghurt.
• One lonely mushroom. The Thai point of the dish is the mixed-mushroom texture — crisp enoki, meaty oyster, springy wood ear. A pot of button mushrooms misses the reason the je version exists.

UK Ingredient Notes

• Galangal (ข่า): fresh or frozen at Thai grocers and bigger Asian supermarkets; jars of sliced galangal in brine work too. Do not substitute ginger.
• Mushrooms: oyster, king oyster, shiitake and enoki are standard in UK supermarkets; straw mushrooms and wood ear (often dried) come from Thai grocers — dried wood ear needs a soak.
• Coconut water: any bottled plain coconut water; or thin the coconut milk with water if you prefer. Coconut shoot (ยอดมะพร้าวอ่อน) is a Thai-grocer item — swap in bamboo shoot or young corn, or leave it out.
• Kaffir lime leaves and lemongrass: fresh at Thai grocers, frozen year-round.
• Tamarind paste (น้ำมะขามเปียก): blocks from Thai grocers, or jars of tamarind concentrate; if using concentrate, start with half and taste.
• To make the chicken version (ต้มข่าไก่ใส่เห็ด, Kapook): swap the tamarind for fish sauce and add sliced chicken at the boiling-water stage, before the mushrooms.

Sources

This recipe is translated from the following Thai-language sources. Where they disagree, we've said so.