Grind dried chilies in a coffee grinder until fine. If using an immersion blender, blend all curry paste ingredients together until fine. If using a mortar and pestle, grind lemongrass, galangal, turmeric and kaffir lime zest (if using) first until fine, adding the dried chilies in once the mixture starts to feel wet. Then add garlic and shallots and pound until fine. Add shrimp paste and pound to mix. Stir fish sauce in at the very end. Using your hands, and I recommend wearing latex gloves for this part, knead together the chicken and the curry paste until thoroughly mixed. Then add cilantro, green onion and kaffir lime leaves and knead it in just until combined.