Sauté the onions in 2 tablespoons of olive oil and 2 tablespoons of butter. When almost translucent, add ginger, coriander, turmeric, saffron, white pepper and kosher salt. Cook for several minutes and remove from pan. Set aside in tagine base.
Add 1 tablespoon of butter and brown the chicken, skin side down first. Season with salt.
Add the chicken stock to the onion and spice mixture. Simmer on the stovetop in the tagine on top of stove burner with a heat diffuser for several minutes. You can't place the clay glazed tagine on direct flame or it will crack and ruin the tagine.
Next, nestle the chicken in the onion mixture, put tagine lid on and place in the oven for 50 minutes.
Remove tagine from oven, remove chicken and keep warm. Next, add the diced preserved lemon, 2 tablespoons of chopped parsley and chickpeas. Stir in 2 tbsp butter, then olives and nestle the chicken back in. Cover and allow to rest for 5 minutes. The chickpeas and olives will be heated through (this is hot).
Serve with a garnish of chopped parsley and preserved lemon quarters on top over couscous or rice.