4 tbsp unsalted butter
1 large onion, thinly sliced
1/4 cup thinly sliced fresh ginger, plus 1 cup slivered fresh ginger for garnish
2 tbsp Thai red curry paste
3 lbs kabocha or butternut squash, peeled, seeded and cut into 2-inch pieces
5 cups water of chicken stock
Two 13.5 oz cans unsweetened coconut milk
2 keffir lime leaves or 1 tsp lime zest
1 large stalk of fresh lemongrass, smashed and cut into 2-inch lengths
2 tbsp light brown sugar
2 tbsp fresh lime juice
1/4 cup vegetable oil
3 large scallions, thinly sliced
a few cilantro stalks for garnish (coriander)
In a large, heavy pot, melt the butter. Add the onion and sliced ginger and cook over a moderate heat, stirring occasionally, until the onion is softened, 7 minutes.
Add the curry paste and cook, stirring, until fragrant, 2 minutes. Add the squash and water/stock and bring to the boil.Cover partially and simmer over low heat until soft, 25 minutes. Add the coconut milk, broken up lime leaves and lemongrass, cover partially and simmer for 30 minutes longer. Discard the lime leaves and lemongrass.
Working in batches, puree the soup in a blender; add it to a clean pot. Stir in the sugar and lime juice and season with salt.
In a medium skillet, heat the oil until shimmering. Add the 1 cup of slivered ginger and cook over moderate heat, stirring, until golden brown and crisp, 5 minutes. With a slotted spoon, transfer the ginger to paper towels to drain.
Reheat the soup; ladle it into the bowls. Garnish with the fried ginger, scallions and a few cilantro leaves (coriander) and serve