In a small saucepan, heat the milk and saffron just to a simmer and remove from heat. Add the butter and let sit until butter is melted.
Meanwhile, in a stand mixer bowl, combine the flour, yeast, potato flakes, salt and sugar. Add milk mixture.
Separate one of the eggs and set the white aside. Add the remaining yolk, whole eggs and vanilla to the mixer bowl.
Mix with a dough hook until a smooth dough forms. Shape dough into a ball and place in a lightly greased large bowl. Cover with plastic and allow to double in bulk, about 1 hour.
Punch the dough down and divide into 16 equal pieces. Shape each piece into a ball and let rest for 10 minutes under a damp tea towel.
Roll each ball into a rope about 12 inches long. Shape into an “S” by coiling up the ends in opposite directions. Tuck a golden raisin into the center of each of the coils. Place bun on a parchment-lined baking sheet and repeat with remaining dough.
Cover and let rise for about 20 minutes until slightly puffed.
Preheat oven to 375°. Whisk the remaining egg white slightly and carefully brush each bun with some of the white. Sprinkle tops of buns with a little pearl sugar, if desired. Bake buns for 15 minutes until golden brown.