17 to 20 (2- to 3-inch-long) prik haeng (dried hot red chiles), halved and seeds discarded
4 tsp Coriander Seeds
2 fresh lemongrass stalks, 1 or 2 outer leaves discarded
1 tsp Whole Black Peppercorns
4 tsp finely chopped Dried Galangal Root
6 (4-inch-long) fresh or frozen Kaffir lime leaves (sometimes called bai makroot), finely chopped
2 Tbsp chopped fresh cilantro roots or stems
5 small shallots, chopped (6 Tbsp)
1/4 cup chopped garlic
15 to 20 (1-inch-long) red prik kii noo (fresh bird’s-eye chiles) or serrano chiles, finely chopped
2 tsp ga-pi (Thai shrimp paste)
1/2 tsp Salt
Cut dried chilies into 1/4″ pieces with kitchen scissors; soak in warm water along with the diced galangal root until mixture is softened, about 20 min. Drain well with a small strainer.
While chilies soak, toast coriander seeds over moderate heat, using a small, dry heavy skillet. Shake skillet intermittently, until coriander is fragrant, 3 minutes or so, then allow to cool. Thinly slice lowest 6″ of the lemongrass stalks and finely chop.
Finely grind toasted coriander and peppercorns with a mortar and pestle (or in mini food processor / spice grinder), then toss together in a bowl with the chopped lemongrass, lime leaves, cilantro, shallot, garlic, fresh chilies, and soaked/strained dried chiles and galangal.
Use the mortar and pestle to mash the mixture in 3 batches, until a fairly smooth paste is formed, 8 to 10 minutes per batch, transferring each batch to a clean bowl. (You can also perform this step using a food processor. If you go this route, add about 1-1/2 Tbsp water per batch of spices.)
Return all of the mashed spices / curry paste to the mortar (or food processor) bowl, then add shrimp paste and salt. Pound (or pulse) until mixture is well-combined, about 1 minute.