4 tablespoons coconut oil or neutral-tasting oil
3 medium shallots, diced
1 (2-inch) piece of fresh ginger, peeled and thinly sliced
1 lemongrass stalk, cut into 3-inch pieces
2 medium butternut squashes (about 4 pounds), peeled, seeded and cut into about 3/4-inch cubes
2 (13 1/2-ounce) cans coconut milk
6 to 8 tablespoons Thai green curry paste, or to taste
3 tablespoons fish sauce
3 to 4 cups water or chicken stock, preferably homemade
Miang kham topping to garnish (see related recipe)
Heat oven to 300 degrees. Melt oil in a large Dutch oven or soup pot over medium-high heat. When oil shimmers, add shallots, ginger, lemongrass and a generous pinch of salt. Reduce heat to low. Cook, stirring occasionally, until shallots are tender and just starting to brown, about 18 minutes.
Add squash, coconut milk, curry paste, 3 tablespoons fish sauce and 3 cups water or stock. Increase heat to high. When liquid comes to a boil, reduce to a simmer and cook the soup covered until squash is tender, about 25 minutes.
Remove soup from heat. Remove lemongrass stalks from pot. Use a hand blender to purée soup. Alternatively, transfer soup in batches to a blender or food processor and purée. Taste and adjust for salt and curry paste. Add water or stock to thin soup to the desired consistency.
Serve soup hot with garnishes.