Sauté the onions in the oil, in a non-reactive soup-pot, over medium heat until softened - about 5 minutes. Add the carrots, grated ginger, salt and pepper and continue to sauté, stirring constantly, for 2 to 3 minutes.

Add the water and bring to a boil. Reduce the heat, cover, and simmer for 20 to 30 minutes, until the carrots are very soft. Stir in the juice.

Place batches of soup in the blender, or use a submersible mixer, and purée the soup until smooth. Serve warm or chilled, with freshly grated nutmeg sprinkled over the top.