Place the beef in a pot. Cut the onion in half and put it in the pot.  Add turmeric and pour in boiling water until it covers the beef; cover the pot with a lid.  Simmer the pot over low heat for 45 minutes (until beef is fully cooked). Shred and mash the beef with a hand blender.  Beat the egg yolk in a pot.  Add the sugar (1/2 cup) to the pot and stir.  Add 5 tablespoons of plain yogurt. (Add more yogurt if the mixture is still thick.) Blend thoroughly until well mixed.  Heat the pot over low heat and keep stirring.  Continue stirring until the mixture becomes creamy.  Add the mashed beef to the pot and continue stirring until well mixed.  Add the saffron to the pot and continue stirring until well blended.  Leave the mixture at room temperature until it cools down, then place it in the refrigerator. Serve cold. Decorate with pistachios and dried barberries.

Serves 4.