How to Make It
In a large saucepan, heat the olive oil until shimmering. Add the chopped shallots, sliced garlic and a generous pinch of salt and cook over moderately high heat, stirring, until the shallots are just starting to brown, about 3 minutes. Add the squash cubes, curry powder, cumin, cinnamon and crushed red pepper and cook, stirring occasionally, for 3 minutes. Add the chicken stock, lemon juice, apple cider vinegar and 3 cups of water and bring the soup to a boil; reduce the heat to moderately low and simmer, stirring occasionally, until the squash is very tender, about 20 minutes.
Working in batches, puree the soup in a blender until smooth. Return the soup to the saucepan. Add the heavy cream and Asian fish sauce and stir over moderately low heat until it is hot, about 5 minutes. Season the soup with salt. Ladle the squash soup into bowls, garnish with the chopped cilantro and serve.