Sift the flour into a very large bowl - remember that the dough will triple in volume. Add the salt, the groung mahlepi and the masticha, if you are using it.
Put the butter in a pan and warm gently to melt it. Add the sugar and heat it very gently until the sugat has dissolved. Remove from the heat and allow it to cool slightly.
In another bowl, whisk the eggs and the milk and then add the sugar/butter mixture. Mix it really well.
Next combine all the liquid ingredients and add the dissolved yeast, and add them all to the flour.
Mix it all together really well with a wooden spoon until you have a well-combined dough.
Cover the bowl with the dough in and leave to rise in a warm place for about 2 hours. It should treble in volume.
After a couple of hours put the risen dough onto the kitchen work surface. Now put some of the extra melted butter on your hands, and knead the dough really well. It should be a soft and buttery, and not stick to your hands.
Now decide how to shape the dough. The most popular shape is a long plait. So divide the dough into two, and then divide each half into three equal parts.
Line 2 baking trays with baking parchment
Make long 'sausages' and, using three for each loaf, make a plait and put on the baking trays. Now cover the loaves and allow them to rise for another few hours. They will treble in size.
When they have risen, put the oven on at 160°, leave it to warm up. Now make the egg glaze.