1. Beat the butter for 5 minutes in the mixer until fluffy.
2. Add the icing sugar.
3. Continue beating until homogenized.
4. Add the granulated sugar, mahlab, mastic, nutmeg, vanilla and orange zest.
5. Keep beating.
6. Then add the milk and gradually one by one the eggs.
7. Then add the baking powder with the flour gradually.
8. Butter and flour a baking pan. Bake at 165 C about 1 hour and 15 minutes.

For the glaze

9. In a saucepan, heat the heavy cream and break the white chocolate into small pieces.
10. Pour in the chocolate pieces and mix with a spatula.
11. Transfer the mixture to a dispenser.
12. Beat the mixture with a hand blender and pour the butter into small pieces.