1In a large saucepan over medium heat, add the oil and warm until hot. Add the onion, garlic, and a pinch of salt and cook, stirring, until it softens, about 5 minutes. Add the lemongrass, ginger, curry powder, and sugar and cook, stirring, until the spices are fragrant, about 30 seconds. Pour in the coconut milk, broth, and fish sauce and bring to a boil.
2Add the chicken, carrots, potatoes, and 1 teaspoon salt, and stir to combine. Cover and simmer, stirring occasionally, until the chicken and vegetables are cooked through, about 30 minutes. Taste and season with salt if necessary. Serve over rice, garnished with the basil.