Make the day before: Boil the sugar and water with zest and juice, + rum (if using). Add raisins and boil for one minute, leave to rest for one day.
Cross mix — make when the dough is proofing: Mix everything together gently until smooth, you don’t want to create gluten. Pop the mix in a piping bag.
Preheat oven to 185°C
Sieve the flour and all the spices into a stand mixer’s mixing bowl.
Dilute the yeast in the water (if you are using instant yeast use 10g instead of the fresh yeast).
Add the egg, water/yeast mix, sugar and salt to the mixing bowl, then the zest of orange and lemon.
Knead in the mixer using a dough hook until the dough comes away from the side of the bowl and will be stiff (if it is sticky dough), add the soft butter and mix until incorporated. Strain the liquid off the raisins and mix into the dough carefully, trying not to break up the raisins. Cover dough with lightly oiled cling film. Keep the spare syrup on the side.
Leave to rest and proof till double in size, knock back and proof again till doubled.
Cut dough into 120g pieces, roll into balls and place in a tray with approx 3cm high edges. Cover with lightly oiled cling film.
Proof until doubled. Pipe a cross on the top and bake in a fan assisted oven for 25 minutes at 185°C. Ovens may vary so keep checking on your buns.
Once ready pull them out and brush some of the syrup left from the raisins onto the top to give you a nice shiny sticky bun.
Allow to cool if you have the will power, cut in half, toast and smother with butter or a generous scoop of gelato.