In a mixing bowl, combine the semolina, potato starch, sugar, mahlab, and butter together and mix well. Add the orange blossom water and begin kneading and working into a soft, pliable dough for about 3-4 minutes. Cover with cling film and refrigerate for 2 hours.
Meanwhile, prepare the fillings. Begin by adding the pistachios to a small food processor along with the sugar and orange blossom water. Whizz for 1 minute to a rough paste. Repeat with all fillings.
Remove dough from the fridge and let sit at room temperature for about 20 minutes before kneading it one more time for a couple of minutes. Divide the dough into three even quantities and roll out each third into a long thin rod-like form. Pinch off small lumps off the dough (about 1 in/2.5 cm pieces) and using the palm of your hands, flatten the dough making sure it is thin but not too thin that it will tear.
Dust ma’amoul mould cavities with semolina and then invert and tap gently to remove excess flour. Flatten the dough gently into the moulds cavity and add the filling associated with the design of the mould’s cavity. Bring the edges together and seal well, flattening it out to create a leveled base for the cookie to sit, pinching off any excess dough. Gently release by tapping the mold on the table or counter to remove the ma’amoul cookie.
The ma’amoul cookie should be clearly stamped with the design. Dust a baking tray with semolina or farina and bake in a preheated oven 200C, until the sides are slightly pinkish in color. It will vary depending on the oven. Bake for 10-15 minutes and about 8-10 minutes for the smaller date cookies. Leave aside to cool then sprinkle with powdered sugar and serve.
Note: There are two different ways of making these cookies. I like to add the filling using the mould because I find it yields more consistent results. However, you could just flatten the dough in the palm of your hand while making a hole in the paste then stuff it with the filling, seal the edges, roll it into a ball then finally press it into the moulds to stamp. If you don’t have the moulds, you could just use a fork to create a design of your choice, that will differentiate the cookies with different fillings from each other.