1. In a bowl, mix the flour, baking powder, vanilla, and mastic. Stir the orange zest with the sugar.
2. Place the butter in a bowl or the bowl of a stand mixer and beat vigorously with a whisk or the K-beater attachment.
3. Add the sugar and continue beating until fluffy. Add the eggs one by one. Add half of the flour. Pour in the orange juice and the remaining flour.
4. Knead lightly with your hands until you have a soft, pliable dough that doesn't stick to your hands. Press it down slightly and cover the bowl with plastic wrap.
5. Refrigerate for half an hour. Preheat the oven to 170°C and line 2 baking trays with non-stick parchment paper.
To shape them:
1. Remove the dough from the refrigerator and shape the koulourakia. Take a piece of dough (30g) and roll it into a 15cm stick.
2. Twist one end from the top towards the center and the other end from the bottom towards the center, creating an S shape. You can also form any other shapes you like.
3. Place the koulourakia on the baking trays. Brush with the egg and, if desired, sprinkle with sesame seeds. Bake in the preheated oven for 20-25 minutes or until golden brown.
