1. Mix the heavy cream, sahlab powder, cornstarch, Arabic mastic and orange blossom, stirring occasionally, over medium low heat, until thick. Set aside to cool in a large plate.
2. Mix the heavy cream, powdered sugar and ready ashta in the cold stainless bowl of the stand mix using the paddle attachment until soft peak forms.
3. Combine the two mixtures and mix for about 3 minutes.
4. Roll out the mixture to a rectangular plate and freeze for 2 hours. Put it again in the food processor and mix for 5 minutes.
5. Repeat the step 4 twice.
6. Roll out the ice cream on a parchment paper and top with pistachios.
7. Wrap it with the parchment paper, roll and freeze again.

Use a rectangular cake mold (step 7) and freeze.