Preheat the oven to 325°F.

Dry the chicken pieces using paper towels, then season them thoroughly with 2½ teaspoons of kosher salt and a generous amount of freshly ground black pepper.

Place a large Dutch oven over medium-high heat. Once hot, add the oil, swirling to coat the bottom of the pot. Working in batches if needed, sear the chicken until it’s evenly browned on all sides, about 6 to 8 minutes per batch. Remove the browned chicken and set it aside on a plate.

Lower the heat to medium and add the scallions, ginger, garlic, lemongrass (if using), and chiles. Stir and cook for 1 to 2 minutes until fragrant and softened. Add the red curry paste, stirring constantly, and cook for an additional minute. Pour in the coconut milk and add the sweet potato chunks, stirring to combine.

Arrange the chicken pieces on top of the sweet potatoes in the pot, ensuring the breast meat is placed on top. Add about ½ cup of water, just enough to bring the liquid level halfway up the sides of the chicken. Bring everything to a simmer, cover the pot, and transfer it to the oven. Let it bake for about 40 minutes, or until the chicken is fully cooked and tender.

While the chicken is cooking, heat a small skillet over medium heat. Add the unsweetened coconut flakes and toast them until golden brown, about 2 to 3 minutes. Then, add the mustard seeds to the skillet and toast for another minute until they begin to pop. Remove from heat, transfer the mixture to a small bowl, and season with a pinch of salt.

Once the chicken is done baking, transfer the chicken pieces and sweet potatoes to a serving platter. Place the Dutch oven back on the stove and simmer the remaining cooking liquid over medium-high heat until it thickens slightly, about 5 to 10 minutes.

Pour the thickened sauce over the chicken and sweet potatoes on the platter. Sprinkle the toasted coconut and mustard seed mixture on top, then garnish with fresh cilantro leaves. Serve with lime wedges on the side for added brightness.