1. Generously salt chicken legs on all sides. Let stand at room temperature for 1 hour.

2. Heat 1 tablespoon fat in the bottom of a stainless steel tagine over medium-high heat. Add 3 of the chicken legs and cook, turning once, 3 to 4 minutes on all sides, until well browned. Remove legs from pan and repeat process with remaining 3 chicken legs. Remove from pan and set aside.

3. Discard all but 2 tablespoons fat from tagine. If fat is burnt, discard and add remaining 2 tablespoons. Place tagine over medium-high heat, stirring often and adjusting heat as necessary, until rich golden brown, about 15 minutes.

4. Meanwhile, remove all racks from oven except for bottom rack so that tagine will fit. Preheat oven to 350 degrees.

5. Add coriander, white pepper, ginger, saffron, and turmeric to tagine; cook, stirring constantly, until spices are lightly toasted, about 1 1/2 minutes. Return chicken legs to tagine; add chicken stock and bring to a boil. Cover tagine and transfer to oven; cook until chicken is tender and beginning to pull away from ends of drumsticks, about 40 minutes.

6. Remove chicken legs from tagine and set aside. Return tagine to stove and simmer over medium-high heat until liquid is thick enough to coat the back of a spoon, about 3 minutes. Season with salt. Add lemons and olive; cook until heated through. Whisk in butter and herbs.

7. Arrange chicken legs on a platter and spoon sauce over them; serve immediately.