Toast the dry spices: In a dry pan over low heat, toast the nutmeg, mace, cardamom pods, cloves, white peppercorns, cumin seeds, coriander seeds, cinnamon stick, and dried chilies. Stir constantly for 8–10 minutes until fragrant and slightly darkened. Remove from the heat and let cool.
Grind the spices: Once cool, grind into a fine powder using a spice grinder or mortar and pestle. Set aside.
Roast the fresh aromatics: In the same pan, dry-roast the galangal, shallots, garlic, ginger, kaffir lime peel, lemongrass, and coriander roots with a pinch of salt. Stir over low heat until deeply aromatic and slightly charred.
Incorporate the shrimp paste: Add the shrimp paste to the pan, stirring briefly to release its aroma. Remove from heat and let cool.
Blend the paste: Blend the roasted aromatics until smooth, adding just enough vegetable oil or water to help the blades turn.
Mix the ground spices into the herb paste and blend again until smooth and fully combined. Store in an airtight container.
Fry the paste: Heat the thick coconut milk in a large pot over medium heat until it just comes to a boil. Add the Massaman curry paste and cook, stirring, until the oil begins to separate and the paste smells fragrant (about 5 minutes).
Add aromatics, chicken, potatoes, and cashews: Stir in the sliced onions until slightly softened. Add the chicken drumsticks, coating them well with the paste. Then add the cashew nuts and cubed potatoes.
Simmer: Pour in the thin coconut milk. Lower the heat and simmer gently for 45–60 minutes, stirring occasionally to prevent sticking, until the chicken is tender and the potatoes are cooked through.
Add palm sugar, tamarind paste, fish sauce, and a pinch of salt. Stir well, then taste and adjust — balancing sweet, sour, and salty flavors.
Serve: Serve hot with steamed jasmine rice.
