Japanese Beef and Potato Stew Recipe

Recipe (makes 4 servings): 1 teaspoon oil, 1 onion, 1/2 lb pork (or beef) thinly sliced, 2 medium potatoes, 2 medium carrot, 1 cup water, 3 tablespoons sugar, 1/2 teaspoon salt, 4 tablespoons soy sauce, 2 tablespoons sake, 3 tablespoons mirin.