The granite mortar (khrok hin) is the most fundamental tool in the Thai kitchen — used daily, for decades, in every household of every region. The making of curry paste by hand pounding predates every alternative by centuries. Thompson learned his paste-making from Thai home cooks and professional cooks over years of study in Bangkok and the provinces — his insistence on the mortar is not romanticism but culinary accuracy.
The making of a Thai curry paste in a granite mortar — the sequential pounding of aromatics from hardest and driest to most moist, each added only when the previous is fully broken down, until the resulting paste is smooth, fragrant, and utterly unlike a blended equivalent. The paste is the curry. The liquid in which it cooks, the protein it coats, and the vegetables that float in it are the setting — the paste is where the dish lives or dies. Thompson is unequivocal: a blender produces a sauce; a mortar produces a paste. The distinction is not philosophical but physical — the mortar ruptures every cell wall and releases every aromatic compound. The blender chops. The two results taste differently, cook differently, and behave differently in hot oil or coconut cream.
The mortar's rupturing of lemongrass cells releases citral (the primary aromatic compound — a mixture of geranial and neral) in a quantity and completeness that a blender cannot achieve. Citral is the lemon-citrus character of lemongrass — and it is a volatile compound that begins to dissipate from the moment of cell rupture. In the mortar, the citral is immediately surrounded by the other paste ingredients and partially absorbed into the fat-soluble aromatic compounds of the galangal and kaffir lime zest — it is 'captured' rather than lost. In a blender, the citral is released and partially lost to the surrounding air before the other ingredients can bind it. As Segnit notes, lemongrass and galangal have a documented aromatic affinity — their shared terpenoid compound families (citral and galangal's acetoxychavicol) amplify each other when combined.
**Ingredient precision — base aromatic components (most curry pastes):** - Dried chillies (for colour and fruit depth): soaked in warm water 15 minutes, drained, seeds and membranes reduced for moderate heat or retained for full heat. Dried chilli varieties matter: phrik haeng (dried red) for the standard paste; phrik chi fa (elongated, milder, for red curry's characteristic colour); phrik khi nu haeng (tiny bird's eye dried, for full heat). - Fresh chillies: bird's eye (phrik khi nu) for heat intensity; long green or red for colour and fruit. - Lemongrass (takhrai): lower 10cm only, outer layers removed, the white-green core sliced thin before pounding. Old, woody lemongrass produces fibrous shreds that will not break down fully in the mortar — use fresh, springy stalks. - Galangal (kha): not ginger. Galangal's flavour compounds (1'S-1'-acetoxychavicol acetate and related phenylpropanoids) are completely distinct from ginger's gingerols — the flavour is piney, slightly medicinal, and clean where ginger is warming and spicy. Galangal cannot be substituted with ginger for a paste. Peel and slice thin. - Kaffir lime zest (peel of makrut): not the juice, not the leaves — the zest, rasped with a fine microplane or scraped from the fruit. The zest carries the fruit's aromatic oils; the leaves provide a different aromatic register. Both are used but at different moments. - Garlic (kratiam): Thai garlic is smaller and more pungent than Western. Adjust: 2 Thai cloves = 1 large Western clove. - Shallots (hom daeng): red shallots preferred — their flavour is more complex than brown shallots. Roasted in their skins (either on the gas flame or in a dry pan) before pounding for many paste styles — roasting sweetens and deepens the shallot character. - Coriander root (rak phak chi): the root, not the stem or leaf. Coriander root has a completely different, more complex aromatic profile than the leaf — earthy, sweet, and aromatic rather than green and fresh. Essential to many Thai pastes; can be simulated with the lower stem but the flavour is noticeably different. - Shrimp paste (gapi): toasted before adding (wrap a teaspoon-quantity in foil, toast in a dry pan or over a flame for 1–2 minutes) for pastes in which the gapi flavour is intended to be deep and smoky rather than raw and sharp. - White peppercorns, coriander seeds, cumin (for specific pastes): dry-toasted before grinding — the same principle as every classical spice preparation. **The pounding sequence (hardest/driest to softest/most moist):** 1. Dried chillies (soaked), salt — reduce to a coarse paste. The salt acts as an abrasive. 2. Lemongrass — add and pound until no fibrous pieces remain. This is the most important step to complete before adding the next ingredient. Any un-broken lemongrass fibre cannot be broken down further with additional ingredients covering it. 3. Galangal — add and incorporate. 4. Kaffir lime zest. 5. Coriander root. 6. Fresh chillies. 7. Garlic. 8. Shallots (or roasted shallots). 9. Toasted shrimp paste (last — its moisture binds the paste). **The verification test:** Thompson's standard — take a small quantity of paste on a spoon. Taste it. The flavour should be complex, balanced between the various aromatics, and smooth in texture — no identifiable pieces of any individual ingredient. Rub a small amount between finger and thumb: it should feel smooth, not fibrous or grainy. Any fibrousness means the lemongrass, galangal, or dried chilli was not sufficiently broken down. Return to pounding. Decisive moment: The complete breakdown of the lemongrass in the mortar — the point at which the pale green fibrous slices have been reduced to a smooth, fragrant mass with no visible individual fibres. This is the paste's most demanding step because lemongrass is the most fibrous of the paste aromatics and the most resistant to the mortar. The temptation is to add the next ingredient before the lemongrass is fully broken — but lemongrass covered with moist ingredients (shallots, fresh chillies) becomes much harder to break down. Complete the lemongrass before adding anything else. Thompson states this directly: rush the lemongrass and spend the rest of the preparation tasting fibre. Sensory tests: **Sound — the pounding process:** Dry aromatics in an empty mortar produce a sharp, clicking sound against the granite. As each ingredient breaks down and releases moisture, the sound changes — from sharp-clicking to a deep, rhythmic, wet thudding. The transition from click to thud signals that the aromatic has been sufficiently broken down. A paste that still produces sharp sounds when the pestle strikes has ingredients not yet fully broken. **Smell — the aromatic sequence:** Each ingredient's aromatic release occurs as it is broken in the mortar. Dried chilli: a deep, dried-fruit and slightly sulphurous release. Lemongrass: an immediate, vivid citrus-herbal explosion that fills the kitchen. Galangal: a piney, medicinal, camphoraceous note. Kaffir lime zest: a sharp, intensely aromatic citrus note with floral depth. Coriander root: sweet and earthy. Garlic and shallot: the sulphur-forward release of allicin compounds. Shrimp paste: pungent and deeply savoury. The progression of these smells is both a guide to the pounding sequence and a quality test — a correctly made paste smells of all of these, harmonised. **Feel — the smooth paste test:** Take a pinch of the completed paste between thumb and forefinger. Rub slowly. A correctly made paste is completely smooth — it feels like a dense, moist cream. No fibre, no grit, no identifiable pieces. If any texture is perceptible: continue pounding, or pass the paste through a fine drum sieve for preparations where the texture is critical (massaman, where the paste should be particularly smooth).
- For high-volume production: make paste in a 500g batch rather than individual portions — the mortar reaches its maximum efficiency at this scale. The paste keeps refrigerated under a film of oil for 2 weeks, or frozen for 3 months. - Add a small quantity of salt at the very beginning of pounding — it acts as an abrasive grit that accelerates the breakdown of the dried ingredients. - If a blender is used (unavoidable at large scale): add 2–3 tablespoons of water to facilitate blending, and accept that the resulting paste will need slightly longer cooking in the wok before it is fully fragrant. The water must cook off before the paste is considered cooked.
— **Fibrous paste that never smooths out:** The lemongrass was not broken down before the wet aromatics were added. Prevention: respect the sequence. If already in this situation: remove the paste from the mortar, press it through a fine strainer, and return only the smooth fraction to the mortar. — **Gritty paste:** Dried chillies not soaked sufficiently, or dried spices not ground finely before adding. Soak chillies a full 15 minutes; use a spice grinder for the dried spices before they enter the mortar. — **Blended paste that smells flat:** The blender does not rupture cell walls — it shears them. The aromatic compounds are not fully released by shearing. A blended paste cooked in the same preparation as a pounded paste of identical ingredients will taste less aromatic and less complex at every stage of the dish. The mortar is not sentiment.
David Thompson, *Thai Food* (2002); *Thai Street Food* (2010)