Clean duck and cut into pieces.
Make a broth by boiling gently for two hours: 10 cups water, 2 tablespoons salt, head, legs and spine from duck, add leek and celery cut into large pieces.
Season duck and fry in hot oil until golden and tender (it doesnt have to be thoroughly cooked).
Remove from pan and save, covered. In the same oil, sauté the garlic, chopped onion and aji or chilli paste. Add the blended coriander, salt and pepper.
Transfer this to a large pan. Add broth, black beer, and the duck pieces.
Finally add peas and red pepper. Cook 8 to 10 minutes more (this can be done in advance).
Fifteen minutes before serving bring the mixture to boil, incorporate rice and mix it well with a wooden spoon. Lower heat and cover pan to continue cooking. Five minutes before rice is done add yellow potatoes. If the mixture becomes too thick add some broth or water. The ideal consistency is that of a thick soup.