In a large pot, combine the squash, onion, sage, thyme, rosemary, bay leaves, ginger, cinnamon sticks, cloves, nutmeg, and salt. Add enough water to cover by 1 to 2 inches, and bring water to a boil over high heat.
Reduce the heat and simmer for 10 to 15 minutes, until the squash is mushy.
Turn off the heat, and use an immersion blender to puree the soup until smooth.
Add the sugar and curry powder, and stir until the sugar dissolves.
Stir in the heavy cream, if using. Season with more salt to taste. Serve warm, garnished with the almonds and dried currants.