Place the beef, onion, ground spices and cinnamon sticks in the base of a tagine or a large, heavy-based saucepan. Pour in just enough water to cover the meat and bring it to the boil. Reduce the heat, cover and simmer for 1½ hours.
Meanwhile, tip the couscous into an ovenproof dish. Stir half a teaspoon salt into the measurement water and pour over the couscous. Stir once to make sure all the grains are submerged in the water, then cover with a clean tea towel and leave to stand for 10–15 minutes.
Add the sultanas, honey and saffron water to the tagine or saucepan, re-cover and cook gently for 15–20 minutes. Season with salt and pepper. Rake a fork through the couscous to break up the grains. Then, using your fingers, rub the oil into the grains until light, airy and any lumps are broken up. Scatter the butter over the top and cover with a piece of damp greaseproof paper. Place in a preheated oven, 180°C (350°F), Gas Mark 4, for 15–20 minutes until heated through.
Serve the couscous with the beef tagine and garnish with parsley.