Whisk the yeast and 2 tsp of the separated caster sugar into the warm milk in a large bowl. Let sit for 10 minutes, until foamy on top (if it doesn't foam, the yeast has died — usually from being old or the milk too hot).

Add the bread flour, remaining sugar, sultanas, cinnamon, allspice, orange zest, egg, melted butter, and sea salt flakes to the yeast mixture.

Mix by hand (or with a stand mixer and dough hook) until it forms a ball. Turn out onto a floured bench and knead for 8-10 minutes until smooth and soft, dusting with extra flour if it sticks (see video for tips).

Oil a large bowl, add the dough, cover with a warm damp tea towel, and proof for 1 hour in a warm spot.

Knock back the dough and knead for 30 seconds. Roll into a 60cm (23-inch) log, halve it, then roll each half out to 40cm (15 inches). Cut each log into 6 pieces (12 total — weigh them for evenness) and roll into smooth balls.

Line a 9x13 inch baking dish with parchment and arrange the balls 3 across, 4 down. Cover with oiled cling wrap and proof for 40 minutes, or until risen by 70%.

Preheat the oven to 180°C (350°F).

Whisk the bread flour and cold water into a smooth paste for the crosses. Transfer to a piping bag with a 3mm round nozzle (or a zip lock bag with the corner snipped off).

Pipe crosses over the buns, starting from the edge (see video). Bake for 20-22 minutes, rotating halfway, until golden brown and cooked through.

Meanwhile, stir the caster sugar and boiling water together until dissolved for the glaze.

Brush the hot buns generously with the glaze and let sit for 5 minutes.

Transfer to a wire rack to cool slightly. Dig in.