In a wide bowl, mix the flour, baking powder, salt, sugar and mahlab (if using). Add the yoghurt and melted butter (or olive oil). Mix well and knead until your dough is fairly soft, around 5 minutes. It shouldn’t be as developed as a bread dough, but softer than an unkneaded dough. You can use a machine for this, but I never bother. Cover and set aside for at least 20 minutes.

Preheat the oven to 190 °C. Line a baking sheet with parchment.

Make the filling by mixing the feta cheese and egg. The eggs help bind the filling and reduces the risk of leakage, but can be omitted for a cleaner cheese flavour.

Divide the dough into 16 equally sized pieces (c. 55 g each). Roll into balls, then press them down until you have flat circles with a diameter of approx 10 cm (4 in). I use my hands for this, making sure the edges are a little thinner than the middle (you don't want the edges, which will be seamed together, to be too thick). If you prefer, you can use a rolling pin.

Divide the filling among the middle of each dough piece. Fold one side over the other, so you get a half moon, pressing out the air as well as you can. Make sure to squeeze the folds together so the seam is completely closed. Trim off any excess dough along the seam. If you like, make a pattern by folding the seam over onto itself repeatedly, or by pressing down a fork. Make sure the seam isn't too thick or wide, or your pastry will be dry.

Place the poğaças on the baking parchment. Brush with the egg yolk whisked with a few drops of water. Drizzle over some nigella seeds or sesame seeds (if you like).

Bake in the middle of the oven until golden, 20–30 minutes. Cool completely before serving (if you can wait).