Although you can use both in this harissa chicken recipe, there are a few noticeable differences. Firstly, labneh is much thicker and creamier than yoghurt as it is double strained (so has less liquid whey) - its consistency is closer to that of whipped cream cheese. It also has a more tangy, salty flavour which is similar to feta (in many Middle Eastern recipes, it is actually viewed as a sort of cheese).