Put the flour, salt, sugar and yeast in a large bowl. Melt 50 g (2 oz) of the butter and stir in along with the coriander, garlic, warm milk and yogurt. Mix with a round-bladed knife to make a dough, adding a dash more milk if the dough is crumbly.
Turn the dough out on to a floured surface and knead for about 10 minutes until the dough is smooth and elastic. Place in a lightly oiled bowl, cover with clingfilm and leave to rise in a warm place for about 1 hour or until doubled in size.
Tip the dough out on to a lightly floured surface and cut into 8 even-sized pieces. Roll each into a ball, cover with a clean tea towel and leave to stand for 10 minutes. Thinly roll out each ball into a large teardrop shape and place on a floured tray.
Melt the remaining butter and brush a little over 2 of the breads. Transfer to a shallow greased baking sheet and place on the upper rack of the halogen oven.
Set the temperature to 250°C (482°F) and cook for about 6 minutes until puffed and golden. Stack on a plate and cover with a tea towel while you cook the remaining flat breads in the same way.