Prepare the Sourdough: Mix 100 g of whole milk at room temperature, 80 g of tsoureki flour, and a sachet of MACM Magic dry yeast. Let it rise for about 20 minutes.
Prepare the Tangzhong: Cook a mixture of 40 g of tsoureki flour and 160 g of whole milk until it thickens, then set aside for 20 minutes.
Combine Mixtures: Combine the sourdough and Tangzhong mixtures in a mixing bowl.
Make the Dough: To the mixture, add 420 g of tsoureki flour, 130 g of granulated sugar, two medium eggs, zest of one orange, 1/2 teaspoon of grated cardamom cacoule, 10 g of grated mahlepi, 1/2 teaspoon of mastic powder, two vanilla pods, and a pinch of salt. Mix well.
Add Butter: After mixing, add 100 g of unsalted butter cut into cubes and mix until the dough is smooth and elastic.
First Rise: Place the dough in an oiled bowl, cover, and let it rise until doubled in size, about 1 hour.
Shape the Tsoureki: Divide the dough into pieces and braid or shape as desired.
Second Rise: Place the shaped dough on a baking tray, cover, and let rise again for about 1 hour.
Bake: Bake in a preheated oven at 160°C (320°F) for 30 minutes or until golden brown.
Apply Melted Butter: Once baked, brush the tsoureki with melted butter to create a protective film and keep it moist.