4 scallions, white and green parts separated and chopped
3 stalks lemongrass, trimmed, bruised, and cut into 2-inch lengths
2 tablespoons chopped fresh ginger
1 tablespoon chopped garlic
1 or more small fresh hot chiles (like Thai or jalapeño), chopped
About 1 pound carrots, chopped
4 cups coconut milk
2 limes: 1 zested and juiced, 1 quartered for serving
1 teaspoon sugar (optional)
1/4 cup chopped fresh cilantro for garnish
1. Put the oil in a large pot over medium heat. When it’s hot, add the white parts of the scallions along with the lemongrass, ginger, garlic, and chiles. Cook, stirring and turning occasionally with a spatula, until the garlic is golden and the scallions and chiles begin to soften, 3 to 5 minutes.
2. Add the carrots and a large pinch of salt and stir to combine. Add the coconut milk, lime zest and juice, and 2 cups water. Bring the mixture to a boil, then lower the heat so it bubbles gently but steadily. Cook, stirring occasionally, until the carrots are very tender, 10 to 15 minutes.
3. Remove the pieces of lemongrass, then use an immersion blender to purée the soup in the pot. Or let the soup cool a little, carefully purée it in a blender (working in batches if necessary), and return it to the pot. (You can make the soup in advance up to this point. Cool, cover, and refrigerate for up to 2 days.) Reheat the soup until it’s hot without letting it come to a boil. Taste and adjust the seasoning, adding the sugar if you think the tanginess and heat need balancing. Garnish with cilantro and green parts of the scallions, and serve with lime wedges.