Cut the whole chicken into about 10 pieces, trim the fat and wash well. Put the chicken pieces in a large pot and put enough water in to cover the chicken. Add the ginger and boil for about 10 minutes on medium heat. Drain off the water and discard ginger, too.
Add water, soya sauce, sugar, Korean hot pepper paste, red pepper powder, garlic and sesame oil. Mix well and cook for 10 minutes.
Peel the potatoes, carrots and onion and cut into 2.5cm x 5cm (1x2 inches). Add the potatoes and carrots to the chicken and cook for 5 more minutes.
Add onion, salt and black pepper, mix well and cook for another 5 minutes. Garnish the soup with the chopped green onions and sesame seeds.