Butterfly or pound chicken breasts to 1/2-inch thickness.
Heat olive oil and butter in a large, heavy, straight sided sauté pan over medium heat until it shimmers, but does not smoke. Add the chicken in batches, making sure to not overcrowd the pan. Season with salt and pepper. Sauté until they are a rich golden brown, about 4-5 minutes per side. Add additional oil and butter as needed. Remove chicken and set aside. Tent with foil.
Drain all but 1 Tablespoon of oil. Add onion and sauté over medium heat until translucent and tender. Add the Harissa Sauce, chicken stock, chickpeas, olives and orange zest. Reduce heat and simmer 10 minutes.
Add chicken to sauce and heat several minutes. Serve over your favorite rice dish. Garnish with parsley.