Place the saffron threads with the salt in a mortar and grind with the pestle, pour over the boiling water and leave to stand for at least 10 minutes. Place the raisins in bowl, pour some hot water over them and then leave them until required.
Sift the flour and pour into a stand-mixer bowl, stir in the sugar and fast action yeast if using. Pour the saffron into the milk and heat in a saucepan to 38C add the yeast and stir.
Fit the dough hook to your stand-mixer and with the machine running on minimum slowly add the milk mixture, then add ¾ of the egg and finally the diced butter, reserving the rest of the egg for glazing.
Mix for 5- 6 minutes or until the dough is silky and shiny.
Tip the dough onto a lightly floured surface and shape into a ball. Clean out the bowl and return the dough to the bowl. Cover with clingfilm and leave in a warm draught-free place for 20-30 minutes or until it has doubled in size.
Tip the dough on to a lightly floured surface and knock it back a couple of times. Divide into 16 pieces, approximately 65g and 70g each.
Roll out each piece so that it is about 30 cm (12") long and curl into tight S shapes. Place each piece on a lined or greased baking sheet, cover loosely and leave for about 30-40 minutes until doubled in size again.
Preheat the oven to 200°C fan. Place a raisin in each scroll of the bun and brush with remaining egg. Bake for 10-12 minutes or until golden brown and sound hollow when you tap the under side.