Heat oils in a large soup pot over medium heat. Add onion, celery, and leeks and cook 4-5 minutes or until tender. Add garlic and cook a minute more. Add sugar, curry, cumin, cayenne, salt, tomatoes, water, and peanut butter and bring to a boil. Reduce heat to simmer and cook about 10 minutes to blend flavors. Stir in scallions, milk or soymilk and heat until warm. Adjust spices to taste.