1. In a bowl, mix the flour, baking powder, vanilla sugar, and mastic. Mix the orange zest with the granulated sugar. In a separate bowl or the bowl of a mixer, place the butter and beat vigorously with a whisk attachment or the paddle attachment. Add the sugar and continue beating until light and fluffy. Add the eggs one by one. Add half of the flour mixture. Pour in the orange juice and the remaining flour. Knead lightly by hand until you have a soft, pliable dough that doesn't stick to your hands. Press the dough slightly, cover the bowl with plastic wrap, and refrigerate for half an hour. Preheat the oven to 170°C (340°F) and line 2 baking sheets with parchment paper.
To Shape Them:
1. Take the dough out of the fridge and shape the cookies. Take a piece of dough (about 30g) and roll it into a 15cm stick. Fold one end over towards the center and the other end under towards the center, creating an 'S' shape. Place the cookies on the baking sheets. Brush them with the egg wash and sprinkle with sesame seeds if desired. Bake in the preheated oven for 20-25 minutes, or until golden brown.
