Heat the soy sauce and water in a large saucepan.
Add the onions and sweet potatoes, mix well, and cook for about 5 minutes or until the onions are softened.
Add the carrots and bell pepper and cook another three to five minutes.
Add the tomatoes, water, beans with any liquid, herbs, peanut butter and curry powder.
Stir to mix, bring it to a boil, then cover and simmer over low heat for another 10 minutes or until the vegetables are fork-tender.
Sprinkle more fresh herbs on top, and serve hot over brown rice.