Mix the flour, salt, yeast and sugar in a bowl. Add the yoghurt, water and oil, knead to form a soft, smooth dough. Cover and leave to rise at room temperature for approx. 1 1/2 hrs. until doubled in size.
Divide the dough into 8 portions and shape into balls. On a lightly floured surface, roll the dough into longish flatbreads (each approx. 15 cm in diameter). Heat the oil in a non-stick frying pan. Reduce the heat, cook the flatbreads in batches over a medium heat for approx. 7 mins. on each side, remove, cover and keep warm.
Mix the mushrooms, onions and oil in a bowl, season. Heat the oil in the same frying pan, fry the vegetables for approx. 7 mins. and spread on top of the flatbreads. Top with the grapes and feta, drizzle with the balsamic glaze and oil.