Prepare the lemongrass: Remove the outer leaves of the lemongrass, then cut the top third off and discard. Use a rolling pin or pot to roll or slightly smash the lemongrass to release its fragrance and flavor. Cut off the root and discard, then mince the lemongrass.
Cook the chicken: In a large pot, warm the coconut oil over medium heat. Once the oil is hot, add in the cubed chicken, season with salt and pepper and sear on all sides until golden brown, about 5 to 7 minutes. Transfer the chicken to a bowl and keep heat in the pot.
In the same pot, add another tablespoon of coconut oil, then the lemongrass and scallions and sauté, stirring frequently, until the scallions begin to soften, about 3 to 5 minutes. Stir in the green curry paste, garlic, ginger, and turmeric; cook for 30 seconds to 1 minute to release the flavors.
Whisk in the coconut milk, chicken broth, soy sauce, and salt. Stir well to combine. Add the chicken, sweet potatoes, bell pepper, and peas and bring to a gentle boil, then reduce the heat to medium-low and simmer, uncovered and stirring occasionally, until the chicken is fully cooked through and sweet potatoes are tender, about 7 to 10 minutes.
Stir in the fish sauce, then taste and add more salt if necessary. Stir in the lime juice.
Garnish and serve: Scoop rice or rice noodles into each bowl, ladle the curry over, and top with LOTS of fresh herbs, scallions, and toasted coconut flakes. Serve immediately and enjoy!
