For the dough:
Place the yeast in a bowl and add the lukewarm water. Stir well with the whisk to dissolve any lumps and slowly add the milk. In a large bowl, place the flour, mastic, mahlep, sugar and salt and mix. Form a hole in the centre of the flour mixture and pour in the oil. Rub the mixture with your fingers to form thick crumbs and gradually start adding the milk and few of the eggs until a soft dough does not stick to your hands. Be careful, as the dough may not need all the eggs. Form the dough in a ball, spread it with a little oil and cover with a towel and then add a blanket on top. Allow it to rest for about 2 hours, until it doubles in volume.
For the filling:
The preparation of the filling should begin two days before. Finely grate the cheeses using the thin side of the grater and place them in a bowl. Cover with a plastic wrap and store in the refrigerator. Occasionally shake the bowl so as to bring to the top the cheeses that were at the bottom. This will help dry the cheeses and thus they will be able to absorb more egg, making your flaounes more fluffy. The evening before, rinse the mint well, cut the leaves and spread them on a towel to dry. Wash the raisins and also spread them on a towel to dry. Pour plenty of water in a saucepan, pour in the sesame seeds, boil for 2-3 minutes and then strain. Place a towel on a wide tray and pour the sesame seeds on top. Cover them well with the towel ends to keep them moist. On the day you will prepare the flaounes, remove the cheeses from the fridge until just cool. At the same time, chop the mint. Add the mastic, sugar, flour, baking powder, raisins and mint to the cheeses and mix well. Then gradually add the beaten eggs, taking care not to add more than necessary. The filling should be able to form medium sized balls that do not break. Cover the bowl of the filling with a towel and place a blanket on top.
To assemble your flaounes:
Cover an oven tray with parchment paper and preheat the oven to 180 ° C. Take some dough (keep the rest covered so it doesn't dry out) and form it into a thick and long ribbon. Cut into 4-5 pieces and roll out with a rolling pin. Using a dessert plate cut round discs of around 12 cm diameter. Spread out the sesame on the tray surface and place each dough disk on top, pressing it down so that the sesame will stick on its surface. Place a medium ball of filling in the centre of each disc and fold the sides inwards without completely covering the filling, forming triangles or squares. Squeeze the corners of your flaounes with a fork to seal well. Place them on a baking tray 3 cm apart and spread the top surface (both dough and filling) with the beaten eggs. You can also sprinkle some sesame on top, if you like. Bake the flaounes in the oven for 45-50 minutes or until well browned.