Preheat the oven at the highest temperature available (220-250 C) and put the eggplants into a roasting tray and put them in the oven. Leave to roast for about 20-30 minutes until they're pretty blackened and soft. Remove from the oven, put in a bowl and cover with plastic foil. Leave to cool.
as soon as they are cool enough to handle, remove the outlayer and put the eggplant inside into a bowl so they can drain off for about 30 minutes
Transfer to another bowl and mash with a fork. Don't make it too fine. You can also do this in a foodprocessor but be careful not to overmix.
Put the yoghurt and the oliveoil into the pureed eggplant and add the garlic too. Put in salt to taste. Stir this well than ad the coriander and the lemon. taste again and add extra salt or lemon if needed