Add lemongrass to the bowl of a food processor and pulse until finely chopped. Add ginger, jalapeños, scallions and garlic and pulse until fine. Add onion and pulse until coarsely chopped. Do not overprocess or mixture will become pureed.
Heat 1 tablespoon oil in a large dutch oven over high heat. Season chicken thighs with salt and add to dutch oven. Sear until deeply golden, about 3 minutes per side. If necessary, saute in batches, adding more oil as necessary. Remove and transfer to a plate.
Lower heat to medium-low and add one tablespoon oil to the pot. Add onion mixture and cook, stirring frequently, for 3 minutes. Add curry powder and continue to cook until vegetables are tender and fragrant, about 5 minutes more. Add chicken stock, coconut milk, rice, and 1 ½ teaspoons salt and nestle chicken into liquid.
Cover and bring to a simmer over low heat. Cover and let cook, about 25 minutes, or until rice is tender, stirring after 15 minutes. Remove from heat and let sit covered, 5 minutes.
While chicken cooks, wipe out the food processor and add cilantro to the bowl. Pulse until finely chopped.
Stir cilantro into the curry and serve, garnished with lime wedges, additional sprigs of cilantro, and toasted coconut shavings.