How to cook
Preheat the oven to 428°F (220 °C). Thoroughly mix the yeast, sugar and milk in a bowl and leave at room temperature for 5-10 minutes for the yeast to activate. Put 1 1/5 cups (280 g) of butter with 2 tablespoons of flour in a blender. Blend the mixture until smooth and transfer it to a bowl.
Add the remaining butter in the blender with the flour and yeast mixture. Blend for 10 seconds until a dough forms. Move the dough onto a floured surface and roll it out. Cover 2/3 of the sheet with butter. Leave about 3/4″ (2 cm) from the edges unbuttered. Fold the unbuttered 1/3 over the others, as if you were folding a bag, then throw the third part over the other two. Store the dough in a plastic bag in the refrigerator for 2 hours.
Roll out the dough back to its previous size. Wrap the three parts one atop the another, roll out and repeat the folding procedure. Put the dough in the fridge for another 1-2 hours. Roll it out again and fold 2 more times. Again, leave the dough in the fridge for an hour and then it will be ready for making croissants.
Roll out the dough into a thin rectangular sheet. First cut it in half and then cut each half into triangles. If the dough is tough, put it back in the refrigerator for a while. Roll out the triangles, put a piece of feta cheese on them, gently roll up the croissants, and wet the tips slightly to prevent sticking. Turn the edges slightly inward to get the true form of croissants.
Arrange the croissants on a tray with baking paper and form their ends in the shape of crescents. Let them rise in a warm area at about 86°F (30 °C). If you decide to let them rise in the oven, be sure to put a bowl of water in. Usually, the croissants take an hour to rise.
15 minutes before baking, brush them with an egg beaten with water. Before putting them in the cold oven, brush them once again. Bake the croissants for 15-20 minutes until golden. Once they puff up well, remove from oven and allow them to cool.