(Poğaça)Pohacha with cheese

1 teaspoon dry yeast 2 teaspoon of sugar70g butter,softened1 egg125g yogurt300g all purpose flour plus for dusting250ml of lukewarm water500g boiled potatoes, peeled and quartered .2 teaspoons salt , plus for boiling the potatoes.1 teaspoon ground black pepper.2 teaspoons chili flakes2 tablespoons of mozzarella or kashar Turkish cheesevegetable oil for brushing1 egg yolk1 tablespoon nigella seeds1 tablespoon sesame seeds Mix the yeast,sugar,lukewarm water set a side for 5 minutes.Whisk the egg,butter,yogurt in a bowlSift the flour in a mixing bowl,make a well pour the yeast and whisk.Add the yogurt mixture and knead vigorously for 10 minutes until you have an elastic dough.Cover the bowl with cloth,place in warm room for 2 hours.place the potatoes in a large saucepan with salted water bring to boil for 15 minutes.Drain the water and mash the potatoes with 1 tablespoon of mozzarella and teaspoon of chili and salt and pepper to taste.add the the remaining chili flakes with mozzarella and salt to the dough and mix.divide the dough to eight pieces.Preheat the oven to 200c/mark 6Flour the surface and the rolling pin or your hands flatten the dough into rounds about 4 inches or 10 cm,add 1 tablespoon of potatoes mixture in the middle of the flatten dough,fold over one side to create half moon shape and press tightly seal the edges.line a baking tray with parchment paper place the pastry and brush the pastry with oil and brush the top with egg yolk sprinkle the seeds and bake for 30 minutes.Serve warm.