Place a small saucepan over medium heat, add in the milk and heat until just warm (don't simmer or boil). Alternatively, this can be done in the microwave in bursts. To be specific, heat the milk to 40°c or 104°f.
In a large mixing bowl, add the yeast, the tsp of the caster of fine sugar that's been separated and pour over the warmed milk. Whisk together until combined and allow to sit for 10 minutes or until the mixture starts to bubble and foam on top (if this doesn't work, it means your yeast has died. This only happens if it's old or you have heated the milk too much).
Into the yeast mixture, add the bread flour, the remaining sugar, sultanas or chocolate chips, ground cinnamon, ground allspice, orange zest, the beaten egg, melted butter and sea salt flakes.
You now have the option to use a stand mixer with a dough hook attachment or use your hands. For this recipe, we're going to use our hands. Using clean hands, mix all the ingredients together until it forms a ball. Dust the working bench with bread flour, ensuring it's well covered and knead the dough for 8 to 10 minutes using the pushdown, fold back and pushdown method until it becomes a smooth soft dough ball (see video for tips). At any stage, the dough starts to stick, dust over a little extra bread flour.
In a large mixing bowl, drizzle in the vegetable oil and wipe it around the bowl with some kitchen cloth. Add in the kneaded dough, place over a warm damp tea towel and allow this to proof for 1 hour in a warmish area.
After 1 hour, dust the workbench again with a light coating of bread flour and tip out the dough. Give it a few punches to knock out the air and knead for 30 seconds to ensure there are no air pockets. Roll the dough into a 60cm or 23-inch log, slice it in half and roll both logs into 40cm or 15 inches. Slice each log into 6 even-sized pieces which will leave you 12 even-sized dough pieces. To be exact, you can weigh each dough ball to ensure they're all the same size. Roll into neat smooth balls.
Spray with oil and line a 9x13 inch deep-sided baking dish with parchment paper. Place in the dough balls, 3 across and 4 down. Place over some lightly oiled cling wrap or plastic wrap and let proof for 40 minutes or until risen by 70%.
Preheat oven to 180°c -350°f.
To make the crosses, add the bread flour and cold water to a mixing bowl and whisk together until it forms a smooth paste. Transfer the paste to a piping bag with a 3mm round nozzle, twist and make sure it's tight. Alternatively, this can be done in a zip lock bag with the corner cut off.
Remove the cling wrap from the dough and pipe on the crosses, make sure to pipe from the very edge of each bun (see video for accurate method). Bake in the preheated oven for 20-22 minutes rotating the tray halfway through.
In the meantime to make the sugar syrup glaze, in a bowl add the caster (fine) sugar and boiling water and mix to combine using a pastry brush.
Remove the buns from the oven and brush over the syrup ensuring they're all well coated. Let sit for 5 minutes.
Gently remove the buns from the baking tray and place them onto a wire rack to cool slightly. Dig in.