Thai curry paste is built through deliberate pounding in a granite mortar, not blending. The mortar CRUSHES plant cell walls, rupturing them and releasing essential oils in a way that a blender's cutting action cannot replicate. A blender chops — fast, clean cuts that leave most cells intact. A mortar crushes — slow, grinding pressure that breaks cells open, releasing volatile aromatic compounds that become part of the paste rather than remaining locked inside intact plant tissue. This is why a mortar paste smells more intensely aromatic than a blended paste, and why it produces a more complex, more deeply flavoured curry.
Quality hierarchy: 1) The order of addition — this is NON-NEGOTIABLE and it is based on hardness. Hard dry spices first (coriander seeds, cumin seeds, white peppercorns — toasted in a dry pan until fragrant, then pounded to powder). Then salt — not for seasoning, but as an ABRASIVE. The coarse salt grains provide grit that helps the pestle grip the next ingredients. Then hard fibrous aromatics (galangal, lemongrass — these are tough and need aggressive pounding against the gritty base to break down). Then softer aromatics (garlic, shallots, chillies — they release moisture that turns the paste wet, which is why they go AFTER the fibrous ingredients are already broken down). Then shrimp paste last — it's already soft and just needs to be incorporated. Each ingredient must be fully broken down before the next goes in. 2) The mortar — a heavy granite mortar with a heavy granite pestle. Not marble (too smooth), not clay (too light for pounding, clay is for salads), not wood (absorbs oils). The weight of the granite does the work. The mortar should weigh at least 3kg. 3) The motion — not straight up-and-down pounding. The correct technique combines a downward strike with a grinding twist against the mortar wall, plus occasional scraping down the sides. The twist is what ruptures cells; the strike alone just compresses. 4) The test — the paste is done when you cannot identify any individual ingredient visually. No fibre strands from lemongrass. No pieces of garlic. No chilli skin fragments. A smooth, homogeneous, intensely aromatic paste that coats the pestle evenly. 5) Time — a proper curry paste from scratch takes 15–20 minutes of steady, focused pounding. This is a workout. There are no shortcuts that produce the same result.
If the paste is done right, the first thing you notice is the smell — it should hit you from arm's length, intensely aromatic, with lemongrass and galangal leading, dried chilli warmth underneath, and shrimp paste providing a savoury bass note. If you have to put your nose in the mortar to smell anything, it's not pounded enough. For green curry paste: the chillies should be bright green bird's eye and long green chillies — the colour of the paste comes entirely from the chillies, not food colouring. Fresh green peppercorns, if available, add a floral sharpness that dried pepper cannot provide. For red curry paste: dried long red chillies soaked in warm water for 20 minutes until pliable. The soak water becomes a flavoured liquid — don't throw it away, use it to thin the paste if needed. Freeze extra paste in ice cube trays — each cube is roughly one portion. It freezes perfectly and loses almost nothing in the thaw. A stash of homemade curry paste cubes in your freezer means a restaurant-quality curry is 15 minutes away at any time.
Adding wet ingredients too early — the paste becomes slippery and the pestle can't grip fibrous ingredients. This is the mistake that makes people give up and reach for the blender. Not toasting dry spices first — raw coriander seed is woody and flat; toasted coriander is nutty and complex. Two minutes in a dry pan transforms the spice entirely. Not pounding each addition fully before adding the next — you end up with chunks of lemongrass in a paste of garlic. Using a food processor and expecting the same result — it's faster but produces a fundamentally different product. If you must use a blender, add a splash of coconut milk (not water) to help the blades catch. Accepting the result after 5 minutes — an under-pounded paste with visible fibres will produce a curry that tastes of individual ingredients rather than a unified, complex whole.