Vegetable Couscous with Harissa

Name: Vegetable Couscous with Harissa
Ingredients: 1/2 cup olive oil, divided; 3 portobello mushrooms, wiped clean, gills removed, and thickly sliced; 1 red onion, quartered; 1 celery root cut into large chunks; 2 white turnips, peeled and quartered; 2 leeks, white and green parts, cleaned and cut into 1/4-inch-thick pieces; 1 medium head cauliflower, separated into florets; 1/2 teaspoon dried thyme; 1/2 teaspoon dried marjoram; 3 tablespoons Ras El Hanout, recipe follows, divided; 5 cups vegetable stock; 2 cups canned chickpeas, drained; 5 cups couscous; Salt, to taste; 10 fresh mint leaves; 2 tablespoons ground ginger; 2 teaspoons ground black pepper; 2 teaspoons ground nutmeg; 2 teaspoons ground allspice; 2 teaspoons ground mace; 2 teaspoons ground cardamom; 2 teaspoons ground cinnamon; 2 teaspoons ground turmeric; 1 teaspoon ground coriander; 1/4 teaspoon ground cloves; 1/4 teaspoon ground red pepper; 1 teaspoon caraway seeds; 1 teaspoon coriander seeds; 1/2 teaspoon cumin seeds; 2 cloves garlic, quartered