Tagine with chicken, vegetables and couscous from the Big Green Egg

Ingredients

• 3 carrots
• 1 large onion
• 2 tomatoes
• 4 chicken thighs (bone-in chicken fillets)
• 1 tbsp olive oil, plus extra for greasing
• 1 tsp ground cinnamon
• 1 tsp ground ginger root
• 1 tsp ground cumin seed
• ½ tsp saffron threads
• 200-250 ml chicken stock
• 16 green olives, unpitted
• 100 g cooked corn (canned)
• 300 g couscous
• 4 naan
• Coriander leaves, to taste