This recipe is adapted from _Sundays at Moosewood Mix in the ginger, salt, and all spices and cook for a few minutes, stirring often. Add tomatoes and sweet potato, stir. Add 1 1/2 cups of water, stir.
Bring soup to a boil, reduce heat, cover, and simmer for 5 minutes. Add 2 cups of the peas and simmer, covered, for 10 minutes. Remove from heat and add remaining 2 cups of water.
Puree in batches in a blender until smooth. return to the pot, add the last cup of peas, and cook on medium heat for 3-5 minutes.