Sift the flour. Wash and peel the potatoes. Cut large potatoes in half. Grate the cheese on a coarse grater. Dust your work surface with flour.
Pour kefir into a large bowl, add butter, salt, sugar and mix well with a whisk. In a separate bowl, combine flour with soda and pour into kefir mass.
Start kneading the dough with a spatula and then continue with your hands. When the dough becomes elastic and does not stick to your hands, wrap it in a bag and leave to rise for 1 hour.
Boil the potatoes and add salt to taste. Crush into puree, add grated cheese and pepper. Mix the filling until smooth.
Knead the dough with your hands into a cake 5-7 mm thick. Place the filling in the middle and form into a “bag”, pressing the edges tightly. Turn the seam side down and knead the dough again into a flat cake with a diameter of 30 cm.
Preheat oven to 220°C. Cover a baking sheet with parchment and grease with vegetable oil. Place the pie and make 2 cross-shaped cuts in the middle. Place to bake for 10-15 minutes.
Grease the finished Ossetian pie with butter, cut into 8 pieces and serve hot.