A warm salad of mixed mushrooms — briefly blanched or stir-fried — dressed with the standard yam dressing (fish sauce, lime juice, palm sugar, fresh chilli) and garnished with shallots, fresh mint, and coriander. Yam hed demonstrates the fundamental yam principle (Entry TH-22) applied to a vegetarian protein base — the mushrooms' umami and textural range replacing the meat's richness, the dressing's acidity and heat providing the same aromatic framework. Thompson covers mushroom yam in the context of the central Thai vegetable preparations, noting that the mushroom varieties chosen determine the dish's character more than any other ingredient.
**Mushroom selection:** Each mushroom variety contributes different texture, flavour, and umami intensity: - King oyster (pleurotus eryngii): firm, meaty stem provides the dressing's best vehicle — absorbs the lime-fish sauce dressing more efficiently than any other mushroom. Slice the stem thick (1cm rounds). - Oyster mushroom (hed nang fa): delicate, tears into natural fronds. Provides textural softness against the king oyster's firmness. - Shiitake (hed hom): deep, complex umami. Caps only — stems too fibrous. - Enoki: fine, delicate, slightly crunchy. Added last — wilts rapidly in heat. - Straw mushroom (hed fang): the traditional Thai mushroom — earthy, slightly nutty. **The cooking:** Two approaches depending on the mushroom combination: - Blanching (for delicate varieties): briefly immersed in boiling salted water for 30–60 seconds, drained, and dressed while warm. - Stir-frying (for firm varieties): in a hot wok with minimal oil, high heat, brief contact — the mushroom should develop slight Maillard colour at the cut surfaces without releasing all its moisture. **The dressing:** Standard yam dressing — fish sauce, lime juice, palm sugar. For mushrooms, the fish sauce quantity is slightly reduced (the mushrooms' own umami means the fish sauce amplifies differently than with less umami-rich proteins). **Timing:** Dress the mushrooms while warm — the warm mushroom surface absorbs the fish sauce-lime dressing more completely than cold mushroom. The same warm-dressing principle as larb (Entry TH-12) and yam nua (Entry TH-22). Decisive moment: The cooking point of the stir-fried mushrooms — specifically, the moment the king oyster slices develop pale gold Maillard colour on both sides (approximately 2 minutes per side at maximum heat) without releasing enough moisture to steam rather than fry. This colour provides the depth that makes mushroom yam more than a simple salad. Sensory tests: **Smell — stir-fried king oyster:** King oyster mushroom at Maillard temperature in a hot wok releases a complex, deeply savoury, nutty-umami smell — from the browning of its proteins and the caramelisation of its naturally occurring sugars. This smell is the quality indicator that the mushroom has been properly seared rather than merely warmed. **Taste — the dressed mushroom yam:** Each mushroom piece should taste of its own variety's character (the deep umami of shiitake, the mild creaminess of oyster, the meatiness of king oyster) simultaneously with the dressing's bright sour-salty-sweet-hot flavour. No single note should dominate — the mushrooms' umami amplifies the dressing, and the dressing makes each mushroom variety more vivid.
David Thompson, *Thai Food* (2002); *Thai Street Food* (2010)