Begin by heating your milk to between 25-35c. Add the milk to a bowl and then add in your sugar and yeast. Mix well to dissolve most of the yeast.

Add the flour, and mix well until it forms into a smooth but loose batter. Cover with plastic or a kitchen towel, and leave somewhere warm until doubled in size and foamy.

Once the starter has foamed up, add the water and olive oil to the bowl, then add the flour and mix well until no clumps of flour remain, and the dough is smooth and no longer shaggy. Cover the dough and allow to rest until it has more than doubled in size.

Flour your worktop generously, then gently pour out the dough. Apply a little flour to the top and sides of the dough, then shape it into an oblong shape. Cut in half, then gently shape each half into a ball.

Prepare a baking tray for each half by lining it with baking paper, place a ball of dough on each one. Shape the dough by stretching it outwards until it's just under 1cm thick, and it has an oval shape about 30 * 20 cm. Dust this with flour, and allow to rest one last time for 25-30 minutes until puffy and doubled in depth.

Preheat your oven to its hottest temperature (240c fan). Add a baking dish to your oven filled with boiling water to create steam.

Make the egg wash by mixing together the egg yolk, water and yoghurt until smooth. Apply the egg wash to the dough gently with a brush, ensuring you cover the entire thing.

With clean hands, press your fingers down into the dough, forming a ring around the entire oval about 2 cm from the edge. Then use your fingers to make diagonal lines in the bread, going from one corner to the one across from it, and on either side of that line. Repeat in the other direction.

Sprinkle with nigella seeds and sesame seeds. Bake until the exterior is a deep even brown all over, about 12 minutes.

Remove from the oven and allow to cool on the tray for 10 minutes, then remove and place on a wire rack. Store in an air tight bag.