Preparation Heat oil in heavy large pot over medium heat. Add onions and sauté until golden, about 15 minutes. Add potato and sauté until light brown, about 10 minutes. Add tomatoes and stir until juices form, about 5 minutes. Add 3 cups water; bring to boil. Reduce heat to low, cover and simmer until potato is tender, about 25 minutes. Working in batches, puree soup in blender until smooth. Return soup to pot. Thin with additional water, if desired. Stir in 1 cup basil leaves. Simmer uncovered 5 minutes. Season soup to taste with salt and pepper. Ladle soup into 4 bowls. Sprinkle each with 1 teaspoon chopped basil.
Preparation Heat oil in heavy large pot over medium heat. Add onions and sauté until golden, about 15 minutes. Add potato and sauté until light brown, about 10 minutes. Add tomatoes and stir until juices form, about 5 minutes. Add 3 cups water; bring to boil. Reduce heat to low, cover and simmer until potato is tender, about 25 minutes. Working in batches, puree soup in blender until smooth. Return soup to pot. Thin with additional water, if desired. Stir in 1 cup basil leaves. Simmer uncovered 5 minutes. Season soup to taste with salt and pepper. Ladle soup into 4 bowls. Sprinkle each with 1 teaspoon chopped basil.