Heat the oil in a 4-quart pot over medium high heat. Season chicken with salt and pepper and sear and cook for 8 minutes on both sides until chicken is cooked. Add the garlic and the sofrito. Cook for 4 minutes and remove.
Add the stock and uncooked couscous to the pot and mix everything well. Cook for 5 minutes in medium heat. Simmer for 5 minutes or until stock is reduced; cover and steam the couscous for 4 more minutes. Garnish with cilantro leaves, serve hot with fried plantains and avocado shavings.