Season duck pieces with salt and pepper. Combine minced garlic and orange juice in a bowl and marinate duck pieces for 1 hour. Remove duck pieces and reserve liquid.
Heat oil in a saucepan and brown duck pieces. Add pisco and bring to a boil until alcohol is evaporated. Add reserved marinade and blended aji and add stock to cover duck pieces. Cook over low heat until duck is tender. Allow to cool.
In a bowl mix onions, aji strips and minced cilantro. Season with lime juice, salt and pepper.
Serve duck pieces on 1 or 2 lettuce leaves and pour some cooling liquid over. Top with the onion sauce.
Garnish with a slice of red hot aji and cooked yucca or cassava.