To make the sauce; melt the butter in a heavy-based saucepan and add the onion, garlic, zucchini, capsicums, pumpkin, potato and turnip. Saute for 10 minutes.
Add half the water to the vegetables and bring to a boil. Reduce the heat and simmer for 30 minutes.
Add chickpeas, tomatoes, Ras el Hanout, salt and the rest of the water.
Stir well and reduce the heat to a simmer. Cook for another 15 minutes. Towards the end of the cooking time for the sauce, prepare the couscous.
To make the couscous; bring water, salt and oil to the boil and remove from the heat. Stirring constantly, add the couscous. Allow the grains to swell for 2 minutes.
Add the butter and heat the grains over low heat for 3 minutes whilst stirring with a fork.
To assemble; pile the couscous on a large pre-warmed serving dish.
Drain some of the liquid from the vegetables, reserving it in a jug to serve as an accompaniment.
Arrange the vegetables over the couscous, pour over some of the stock, and serve immediately.