Prepare and Cook the Chicken Soak the saffron threads in 1/2 cup of hot water. In a mortar, pound the garlic and salt to a paste and then blend in the butter, smen and remaining spices. Gradually stir in the hot saffron water and scrape the mixture (use a spatula – you don't want to waste any of the seasoning!) into a tagine base. Add the chicken pieces to the tagine, skin side up, and rub a bit of the butter mixture on the skin. Set the tagine aside at room temperature for about an hour.
Cover the tagine and place it (a diffuser is recommended) over medium-low heat. Once you hear the tagine simmering, leave it to cook, undisturbed, until the chicken tests tender, about an hour.
While the chicken is cooking, prep the remaining ingredients, as you'll want them ready to work with right after the chicken cooks. Mix the olives, parsley, cilantro and preserved lemon in a small saucepan and set aside. In a bowl, beat together the eggs with a little salt and pepper and set aside.
Broil the Chicken and Make the Egg Sauce When the chicken is tender, transfer the chicken pieces, skin side up, to a broiler pan. Preheat your broiler.
Skim the fat off the sauce that remains in the tagine, reserving about 1/4 cup of the fat. Pour the skimmed sauce from the tagine into the saucepan with the olive and parsley mixture.
Return the unwashed tagine to medium-low heat. Add 2 tablespoons of the fat to the tagine, along with the grated onion. Cook the onion, stirring occasionally, about 10 minutes, until lightly caramelized. Transfer the cooked onions to the saucepan with the sauce, olives and parsley and stir to combine. Place the saucepan over medium heat to reheat the sauce, and then keep warm over low heat.
Brush the chicken with the remaining reserved fat and place about 6 inches under the broiler for 5 to 10 minutes to brown and crisp the skin. Keep the chicken warm while you finish making the sauce.
Place the unwashed tagine over medium-low heat and add the two tablespoons of butter. When it has melted and is foamy-hot, add the beaten eggs. Cook, stirring and scraping constantly, until the eggs begin to thicken. Gradually stir in the lemon juice while continuing to cook the eggs to a creamy consistency.
Immediately remove the tagine from the heat and fold in the warm sauce. Taste and adjust seasoning. Place the chicken, skin side up, back in the tagine (spoon some of the sauce over the chicken if you like) and cover. Leave to stand off the heat for 5 minutes or longer while the egg sauce continues to thicken. Serve directly from the tagine; Moroccan bread should be offered to scoop up the chicken and sauce.
