1. Heat 3 tablespoons olive oil in a large pot over medium-high heat. Season mutton chops and chicken drumsticks with salt and pepper; cook in batches with onions in the hot oil until browned, about 2 minutes per side. Transfer to a large plate.

2. Scrape the bottom of the pot with a wooden spoon to release browned bits. Return mutton chops and chicken to the pot. Pour in enough water to cover; add turmeric, cumin, and coriander. Cover and bring to a boil. Reduce heat to medium; simmer for 20 minutes.

3. Stir potatoes, turnips, and carrots into the pot. Simmer, covered, until vegetables start to soften, about 10 minutes. Mix in tomato paste and ras el hanout; cook for 10 minutes. Stir in chickpeas, zucchini, and cilantro; continue cooking, covered, until zucchini is tender, about 5 minutes.

4. Bring 3 cups water to a boil in a saucepan; remove from heat and stir in couscous and butter. Cover saucepan and let stand until water is absorbed completely, 5 to 10 minutes. Fluff couscous with a fork and stir in 1 tablespoon olive oil. Transfer to a serving dish.

5. Ladle 2 scoops of cooking liquid into a bowl; mix in harissa until smooth.

6. Scoop vegetables onto a serving plate. Scoop mutton and chicken onto a separate plate. Serve alongside couscous, harissa sauce, and remaining cooking liquid in the pot.

Cook's Notes:

For homemade ras el hanout, mix: 1 teaspoon ground cumin, 1 teaspoon ground ginger, 1 teaspoon ground turmeric, 3/4 teaspoon ground cinnamon, 3/4 teaspoon freshly ground black pepper, 1/2 teaspoon ground white pepper, 1/2 teaspoon ground coriander, 1/2 teaspoon ground cayenne, 1/2 teaspoon ground nutmeg, and 1/4 teaspoon ground cloves (optional).

Harissa can usually be found in Mediterranean stores or butchers.