Thinly slice 3 onions and finely chop the remaining onion with the fresh coriander and fresh parsley.

Rub the chicken thighs with ground turmeric, ground ginger, paprika, and salt. Place them in a mixing bowl.

Add the chopped onion-herb mixture, olive oil, and water to the chicken. Marinate for at least 60 min.

Dissolve the saffron in a little water. Heat olive oil in the tagine over medium heat.

Cook the sliced onions, garlic, and a little fresh coriander until the onions are translucent. Add the diluted saffron.

Place the marinated chicken thighs and all of their marinade over the onions. Cover and cook over medium-low heat for 40 min.

Cut the potatoes into fries and soak them in water for at least 30 min. Drain them thoroughly in a colander.

Remove the chicken thighs from the tagine. Stir the green olives and preserved lemon into the reduced sauce.

Place the chicken thighs in an oven dish and brush with butter if desired. Roast at 180°C / 350°F for 20 min until lightly browned.

Fry the drained potatoes in batches until crisp. Let the fries dry for 10 min between each of the three frying rounds.

Return the roasted chicken thighs to the tagine. Serve with the fries and remaining fresh coriander.

Cook the fries in 3 batches, letting them dry for 10 minutes after each batch.

Return the chicken to the dish and serve with the fries on top and fresh coriander.