Place milk, maple syrup and egg in a bowl. Whisk to combine.
Add sourdough starter, spices and zest. Whisk gently to combine.
Add flour and fold in until a sticky dough has formed, Cover with tea towel and leave to rest for 20 mins.
Lightly dust your work surface with flour. Place the dough on the work surface and fold in the raisins and salt. Knead until a soft dough forms.
Divide into 12 even balls and place close together on a baking tray. Cover with a tea towel and leave to rise for 4-8 hours depending on your climate.
Once the buns have risen together, whisk egg and use to glaze the buns using a brush..
Gradually add water to flour until a smooth pipeable paste forms. Place in a piping bag. PIpe crosses over the buns.
Bake in oven at 200 degrees C for 30-40 mins until golden brown.