Mix dry ingredients: In a large mixing bowl, combine 80% of the flour (roughly 4 cups of flour), yeast, mastiha, mahlepi, and salt. Stir well to ensure everything is evenly mixed.
Prepare tahini mix: In a separate cup, whisk the tahini into warm water until it dissolves. Add this mixture to the dry ingredients.
Add orange juice: Pour the orange juice into the bowl and mix until a dough begins to form.
Knead the dough: Lightly flour your workbench with some of the reserved flour. Knead the dough for 5 minutes, incorporating the rest of the flour as needed until the dough is smooth and non-sticky.
Let the dough rise: Place the dough in a clean bowl. Cover it with a towel or plastic wrap and leave it in a warm spot for about 1 hour, or until it doubles in size.
Prepare sesame seeds: While the dough rises, boil the sesame seeds in a saucepan filled with water. Once the water starts bubbling, remove the pan from heat and drain the seeds. Then spread them out onto a clean kitchen towel.
Shape the paximadia: Punch down the dough to release air. Divide into smaller portions, rolling each into balls, and keeping them covered to avoid drying.
Roll and cut: Roll each portion into a stick about 1 cm in diameter. Use a sharp knife to cut each stick into 15 cm long pieces.
Coat in sesame: Roll each piece in sesame seeds, ensuring they’re fully coated. Place the coated sticks in a single layer on a baking tray lined with parchment paper. Cover them to prevent the unbaked dough from drying out. Let them rise for another 15-20. They will puff up and retract slightly to about 12 cm in length.
First bake: Preheat the oven to 160°C (fan-forced). Bake the paximadia for 25-35 minutes, or until they are lightly golden. Let them cool for 30 minutes.
Second bake: Reduce the oven temperature to 100°C (fan-forced) and bake for another 1-2 hours until they’re fully dried and crispy. Test one or two to check the texture. The lower temperature is crucial to allow further cooking without further browning.
Cool and enjoy: Once fully baked, remove the paximadia from the oven and let them cool. Serve and enjoy!