Place the flour, sugar, spices, and lemon zest into a large bowl and mix well. Add the salt and yeast, keeping them on opposite sides of the bowl.
Melt the butter in a small pan and gently warm the milk in a separate one. Pour the melted butter and half the tepid milk into the dry ingredients. Add the egg and use your hands to combine everything, drawing in the flour from the edges of the bowl. Gradually add the remaining milk until a soft, pliable dough forms — you may not need all the milk.
Turn the dough onto a lightly floured surface and knead by hand, gradually working in the sultanas and mixed peel. Continue kneading for about 10 minutes until the dough becomes silky, elastic, and forms a smooth ball. (You can also knead the dough in a food mixer fitted with a dough hook.) Lightly oil a large bowl, place the dough inside, cover with cling film, and leave it to rest in a warm spot for about 1½ hours, or until doubled in size.
Once risen, turn the dough out onto a lightly floured surface. Knock back the dough by gently kneading for another 5 minutes. Return it to the bowl, cover with cling film, and leave in a warm place for another hour, or until doubled in size again.
Turn the dough out onto a floured surface and divide it into 12 equal pieces, shaping each into a smooth ball. Line 1–2 baking trays with parchment paper and arrange the balls on the trays, placing them fairly close together and flattening them slightly.
Place each baking tray inside a large, clean polythene bag, ensuring the bag doesn’t touch the buns. Leave them to prove for 40–60 minutes until they’ve doubled in size.
Preheat the oven to 220C/200C Fan/Gas 7.
For the topping, mix the flour with 100ml/3½fl oz water in a bowl to create a smooth paste. Transfer the paste into a piping bag.
When the buns have risen, carefully remove the polythene bags and pipe a cross on each bun.
Bake for 15–20 minutes until the buns are pale golden-brown, rotating the baking trays halfway through if needed.
Melt the golden syrup in a small pan and, while the buns are still warm, brush them with the syrup to create a lovely shine. Transfer to a wire rack and leave to cool completely.