Gaeng Liang (Thai Vegetable Soup with Shrimp Paste and Basil)

Gaeng liang builds its depth from fermented ingredients rather than aromatics or fat. The combination of dried shrimp and shrimp paste creates a double layer of umami: the dried shrimp contribute a concentrated, slightly sweet brininess, while the fermented paste adds a deeper, funkier savory base. Together, they give the broth a complexity that belies the short ingredient list.

White peppercorns provide the only heat in the traditional recipe, and they do it differently from chilies. Piperine, the active compound in pepper, activates different receptors than capsaicin, producing a warming, tingling sensation rather than a burning one. This gentler heat is what makes gaeng liang feel soothing rather than aggressive, and it is one reason the soup is considered restorative in Thai food culture.

The vegetables are staggered into the pot by density, a simple but important technique. Pumpkin and corn go in first because they are dense and starchy. Chayote and luffa follow because they cook faster and turn mushy if overdone. This staging means every vegetable reaches its ideal texture at the same time, which is the difference between a carefully made gaeng liang and a pot of overcooked vegetables in broth.

Sweet basil added off the heat preserves its volatile aromatic compounds, particularly linalool and eugenol, which would break down and dissipate if simmered. The residual heat is enough to wilt the leaves and release their fragrance into the broth without destroying the delicate top notes. This is the same principle behind adding basil at the end of a green curry or finishing tom yum goong with lime juice off the heat.

Vegetables: The vegetable selection in gaeng liang is highly flexible. Traditional options beyond those listed include ivy gourd (tamlueng), angled loofah, wing beans, ash gourd, and pea eggplant. For Western-market substitutions: zucchini works well for luffa, butternut squash for kabocha, and kohlrabi or turnip for chayote. The key is to include a mix of textures, something dense and starchy, something crisp, and something that cooks to a soft texture.

Protein: Prawns are the most common addition, but the soup is also excellent with no protein at all, purely as a vegetable broth. Some regional versions include small pieces of freshwater fish, crab meat, or sliced pork. For a richer variation, add 100 g of cooked crab meat in the last minute of cooking.

Lemongrass in the paste: Not all versions include lemongrass. Pailin Chongchitnant's version omits it, relying solely on shrimp, shrimp paste, shallots, and white pepper for the paste. Including lemongrass, as Nart's version suggests, adds a citrusy layer that some cooks prefer. Both approaches are traditional. Try it both ways and decide which you prefer.

Vegetarian or vegan: Replace dried shrimp with 15 g dried shiitake mushrooms (soaked and pounded). Replace shrimp paste with 10 g white miso or fermented soybean paste. Use vegetable stock. Replace fish sauce with soy sauce or mushroom sauce. The character will be different, but the peppery, basil-fragrant broth will still be satisfying.

Spice level: For more heat, add 2 to 3 fresh green Thai chilies to the paste and pound them in with the peppercorns. This moves the soup closer to a jungle curry in spirit while keeping its distinctive shrimp paste base. Some cooks in Thailand's southern regions do add chilies as a matter of course.

Richer variation: For a version with slightly more body, stir 60 ml of coconut cream into the finished soup just before adding the basil. This is not traditional but produces a pleasant, lightly creamy broth that bridges the gap between gaeng liang and a light coconut curry.

Gaeng liang is a communal dish, meant to sit at the center of a Thai table alongside rice and two or three other preparations. Its light, peppery character makes it an ideal counterpoint to richer dishes. Pair it with green curry for a study in contrasts: one rich and coconut-based, the other lean and broth-forward. It also works beautifully alongside jungle curry, another coconut-free preparation, creating a meal that is vegetable-heavy and restorative.

For a complete Thai soup-centered meal, serve gaeng liang with tom yum goong and steamed jasmine rice. The two soups share a love of aromatic herbs but approach them from very different angles, one sour and fiery, the other peppery and gentle. Gaeng som is another natural companion, offering tartness where gaeng liang offers warmth. The Vietnamese sour soup canh chua shares a similar spirit of vegetables in a clear, flavored broth and makes an interesting cross-cultural pairing.

For a simpler meal, gaeng liang with a plate of rice and a side of khao tom (Thai rice soup) makes a light, nourishing dinner. A small plate of raw vegetables and a dipping sauce rounds out the table without competing with the soup's delicate flavors.

Refrigerator: Store in an airtight container for up to 3 days. The vegetables will soften further as they sit, which is acceptable but changes the texture. Keep the basil in the broth; it will darken but continue to flavor the soup. Store rice separately.

Reheating: Warm gently in a saucepan over medium-low heat until the broth reaches a simmer. Avoid boiling vigorously, as the pumpkin may break down into the broth. Add a few fresh basil leaves just before serving to refresh the aroma.

Freezing: Gaeng liang freezes adequately for up to 1 month, though the vegetable textures will soften noticeably upon thawing. The luffa in particular becomes very soft. If you plan to freeze, consider slightly undercooking all vegetables. Thaw overnight in the refrigerator and reheat on the stovetop. Stir in fresh basil after reheating.

Make-ahead paste: The pounded paste can be made up to 2 days in advance and stored in a sealed container in the refrigerator. This makes the active cooking time very short, essentially just simmering vegetables in broth.