Lightly grease an ovenproof dish with butter or oil.
In a blender or food processor (I used a hand blender), puree cheese until as smooth as possible.
Add the butter, salt and pepper and blend in thoroughly.
Lay one-third of the potatoes in the ovenproof dish and top with one-third of the cheese mixture. Lay down another third of potatoes and cheese, followed by the last third.
Cover the dish with foil and bake until the potatoes are tender, about 1- 11/2 hours.
In a bowl, whisk together the eggs and yoghurt and season with salt and pepper.
Pour over the potatoes and bake, uncovered, until the topping is puffy, golden and set, about 20-30 minutes.
Recipe by Planet Veggie at https://www.planetveggie.co.uk/expedia-world-on-a-plate-vegetarian-bulgarian-recipes/