In a bowl, combine the sifted flour, salt, vanillin, sugar, half the egg, and the dry yeast dissolved in warm milk.
Knead the dough with a hook attachment or by hand, adding the vegetable oil toward the end of kneading. Shape into a ball, cover with plastic wrap, and leave in a warm place for 1.5 hours.
For the filling, mix the ground chicken with the onion, spices, and herbs.
For each portion, take 80 grams of dough and 60 grams of filling: form a flatbread, place the filling in the center, pinch closed, then flatten by hand into a round, making a small hole in the center.
Let the shaped flatbreads proof for 30 minutes, brush with beaten egg, and sprinkle with herbs.
Bake for 30 minutes at 180 °C, and let the finished kubdari cool slightly.