Add sliced potatoes to a pot of cold water and bring to a boil. Simmer 5–7 minutes until slightly tender, then drain. This ensures the potatoes cook evenly in the curry without turning mushy.
In a medium pot, heat coconut oil and toast coriander and cumin seeds for 2 minutes. Add shallots and ginger, then cinnamon, cardamom, cloves, and nutmeg, stirring to release aromatic flavors. This forms a flavorful curry base.
Stir in Thai red curry paste until fragrant. Pour in coconut milk, mixing thoroughly. Add parboiled potatoes and simmer for 10 minutes to combine flavors and thicken the sauce.
Add sliced chicken, fish sauce, brown sugar, tamarind paste, and peanut butter (if using). Simmer 5 minutes until chicken is cooked through and opaque. Taste and adjust seasoning as needed.
Serve curry over jasmine rice, topped with fresh spinach, cilantro, roasted peanuts, lime wedges, and red chili slices for a vibrant and flavorful presentation.