In a non stick frying pan, add the cumin and coriander seeds. Cook over medium heat to toast, 2 to 3 minutes or until aromatic. Remove from the pan, add to a pestle and mortar or spice grinder and blend to a powder.
In a mixing bowl, combine the lamb mince, cumin, coriander, ras el hanout, seasoning, breadcrumbs, egg, garlic, lemon juice and chopped mint. Mix really well using your hands.
Once mixed well, shape into meatball shapes (the size of a ping pong ball) and place on a plate. Cover and place in the fridge for at least 1 hour or overnight.
Heat a little oil (not too much as the lamb mince is quite fatty) and gently pan fry the meatballs in batches until cooked through, about 25 minutes. Keep warm while cooking in batches.
Ten minutes before ready to serve, prepare the couscous. Put the couscous in a bowl, add a knob of butter and 1 heaped teaspoon harissa paste. Pour boiling water over to cover (500ml, or according to packet instructions), stir well and leave to soak.
Make the yoghurt sauce by combining all ingredients. Start with a little harissa and increase the amount according to taste.
When ready to serve, stir through some freshly chopped coriander and fluff up the couscous with a fork and place a portion on a plate. Add the meatballs (7 per person depending on size).
Drizzle over the meatballs some yoghurt, harissa, lemon zest and chopped mint. Serve.
Nice also served with flatbreads and a cucumber and red onion salad.