Soak eight wooden skewers in water for 20 minutes, to stop them burning.
Using your hands, mix the meat in a bowl with the onion, coriander, mint and plenty of seasoning. Shape into 8 sausages, about 10cm long, then thread a bamboo skewer through the centre of each.
To make the sauce, heat the oil in a pan, add the garlic and briefly fry. Add tomatoes, harissa, sugar and seasoning. Simmer, uncovered, for 15-20 mins until sauce has thickened.
Grill the kofte for 6-8 mins, turning until they are nicely browned (be careful not to burn the skewers). Spoon the sauce over a warm platter, drizzle over the yogurt and put the kofte on top. Scatter with pine nuts and serve with pittas or couscous (recipe, below).