Heat oil in a flameproof casserole. Add lamb and chicken. Brown for 10 minutes, in batches if necessary. Season with salt and pepper to taste.
Add all remaining ingredients to the casserole, except for the couscous. Cover and cook over a low heat for 1 hour.
To serve, place a serving of the cooked couscous on each plate. Top with the stew, or let your guests serve themselves. For added heat, serve with a little harissa paste on the side of your plate, and add to taste.
You can also add other vegetables in season, like turnip (thickly sliced), broad beans, runner beans, haricot verts.
Delicious. I substituted one and a half chorizos as it's impossible to find merguez locally... but it worked perfectly well. I also chopped up 4 boneless lamb steaks, and used 8 chicken thighs. Two parsnips also made it in. But it was as good as in a restaurant. - 21 Oct 2013