Let the raisins soak in rum or some other liquid (at least 30 min)
Melt the butter, pour in the milk and heat up to body temperature (37°C or 100°F)
Grind the saffron with the teaspoon of sugar in a mortar and add to the milk
Crumble the yeast into a separate bowl, add the pinch of salt, the sugar and the lukewarm water then stir it together
Pour in the milk and add the egg while stirring it together
Place all the above used ingredients in a stand mixer
Add the flour gradually while stand mixer is stirring on low speed. You might need to add more flour to make it possible to work with the dough without it sticking to all of your fingers.
Then add most of the raisins to the mixture but leave a few for decoration (32 raisins if you make 16 buns)
Work the dough with the stand mixer (or by yourself if you don't have one)
Cover the bowl and let the dough rise for 1 hour or a little more (up to 1½ hours)
Heat up the oven to 260°C (500°F)
Cover a baking tray with parchment paper
Flour a working area and then knead the dough gently a few times
Split the dough in 16 pieces and roll them to long thin strips that you then curl in an S-shape, but make a few extra circles to make them look better than in my picture ;)
Place them on the baking tray with around 1 cm space between (we want them to grow together a little to keep them juicy)
Place one raisin in each end of the bun and press it in so it does not stick out, but is still visible
Place a kitchen towel over the tray and wait for 10 min before brushing them with a whisked egg
Put the tray in the oven for roughly 4-6 min (watch them carefully since the size of the buns and your oven might change the required baking time. They should receive a light brown colour)
As soon as you take them out, cover with a kitchen towel and let them cool down