For the buns
500g bread flour
9g fine sea salt
113g unsalted butter- cut into 1cm cubes
100g active sourdough starter
1 large egg
80g raisins chopped
2 tsp vanilla extract
3 tsp mixed spice
For the glaze
50g plain flour
pinch baking powder
20 ml milk
1 tsp caster sugar
Scald milk in pan and remove. Cut the butter into 1cm squares and add to the milk. This will cool the liquid, wait until blood temperature, about 38°C
Mix the flour sugar and salt in a stand mixer, add the warm milk, starter and egg to the bowl, and mix for 1 min on level 3. Then with your hands work the dough to a rough ball incorporating any dry bits of four at the bottom. Cover with cling film and leave for 1 min
Meanwhile chop the raisins and combine with the vanilla extract. Allow to soak.
After the dough has rested add the raisins, along with any liquid and the mixed spice, and using the dough hook mix on a low speed (3 on a KitchenAid for 8 min). If the dough starts to climb up the side of the bowl, stop the machine and push it back down. The dough will be supple and smooth when finished. It should not stick to your hands, if it does add a sprinkle of flour.
Cover the bowl and rest overnight at room temp (20°C) for 12-18 hours when it has tripled in size.
The following day, oil a 9×13 inch pan. Remove the dough onto your work surface, no need for flour. Cut the dough into 12 equal pieces (they should be 92g per bun)
Shape the balls, buy working with one piece at a time (ensure the remaining a covered with some oiled cling film). Simply fold all the sides toward the centre, and bring together like a money bag. Flip it over, and keep on the surface, and roll it into a ball with the palm of your hand. Try and keep tension in the dough. Place the balls into the pan, evenly spaced, 3 across and 4 down.
Cover the pan with cling film, and let the buns rise at room temperature until the dough had doubled in size. This can take up to 2-3 hours. The dough should look puffy and plump when ready. It very important to not rush this step as the buns will be dense.
Preheat your oven to 200C
To make the crosses for the top of the buns, sift flour and baking powder into a bowl. Stir in the oil and enough cold water to make a loose pipeable paste , put into a piping bag ready for use.
Once the buns have risen and doubled in size, mix the milk and caster sugar and lightly brush the buns lightly, score a 1mm shallow cross on the top of each bun, and then pipe a cross on the top
Place buns in the oven, and after 5 mins reduce the heat to 180. and bake for 25-30 mins. Half way through the bake, lightly brush the buns with the milk and sugar.