Tom Yum Paste

Combine the sliced lemongrass, galangal, kaffir lime zest, and salt in a heavy mortar. Begin pounding with a firm downward rhythm, rotating the pestle to drag fibers into the center. These aromatics are extremely fibrous — the lemongrass in particular has woody cell walls that must be completely crushed to release their volatile oils. Pound for 8–10 minutes until no visible strings remain and the paste smells explosively of lemon, pine, and something vaguely medicinal. Add a splash of water if it becomes too dry to pound effectively.

Drain the soaked chilies and squeeze out excess water. Add the chilies, shallots, and garlic to the mortar. Continue pounding, working each addition in gradually — add the new ingredient, pound until integrated before adding the next. The paste will turn from pale yellow to a deep brick-red as the chilies incorporate. Work for another 8–10 minutes until the mixture is unified and smooth. The shallots and garlic will break down more easily than the initial aromatics.

Unwrap the toasted shrimp paste from its foil and add it to the mortar along with the crumbled kaffir lime leaves. Pound to fully integrate — the shrimp paste will add a fermented, deeply umami note that transforms the paste from simply spicy-aromatic to complex and savory. Add the fish sauce last and fold it in with a few strokes of the pestle rather than pounding. Taste: the paste should be intensely concentrated — hot, sour-aromatic, salty, and oceanic. When diluted in broth (1 tablespoon per 200 ml), it should produce a balanced tom yum. Store under a thin layer of oil in the refrigerator for up to 2 weeks, or freeze in tablespoon-sized portions.