In a 4-quart heavy saucepan bring water to a boil and add bouillon cubes, stirring until dissolved. Add beans and simmer, stirring occasionally, 15 minutes. In a heavy skillet heat oil over moderately high heat until it just begins to smoke and stir-fry carrots until crisp-tender, about 3 minutes. Stir carrots into soup. In a small bowl stir together miso and 1/2 cup hot broth until combined will and stir into soup. Bring soup just to a boil, stirring occasionally, and stir in scallions and pepper to taste. Each serving about 431 calories and 4 grams fat (8% calories from fat).