To make the tangzhong, put the flour and water in a small saucepan and whisk over medium heat until the roux thickens. When the whisk leaves a trail of lines on the surface, it is ready. Put in a small bowl and place cling film directly on the surface to prevent a crust forming. Set aside to cool.
To make the dough in a stand mixer, add the flour, sugar, salt, milk powder, spices and zest to the mixing bowl. Make a well in the centre and add the starter, milk and egg. Start mixing using the dough hook and add the softened butter once the dough forms a ball.
Keep mixing until the dough passes the windowpane test (stretch it in your hands - it should form a thin membrane that is almost transparent without tearing). This can take up to 15 minutes. Place the dough in a greased bowl, cover with clingfilm and prove for an hour or until double in size.
Grease a 20cm(8in) loaf tin and line with baking paper, letting the excess paper hang over the sides.
After the proving, tip the dough on a floured worktop, knock it back and knead in the mixed peel and chocolate buttons until they are incorporated into the dough.
Divide the dough into 6 equal portions. Roll each portion into a ball and place into the prepared tin. Cover with greased clingfilm and set aside for an hour until doubled in size.
Preheat oven to 180C (350F). Brush the loaf with the egg wash.
Mix the flour and milk in a small bowl until you have a thick but pourable paste. Transfer to a piping bag and pipe a cross onto each round of hot cross bun loaf.
Bake for 45-50 minutes until the loaf is risen and a deep golden colour. Cover with foil after 20 minutes if it is colouring too rapidly.
Heat the apricot jam until runny and brush all over the loaf to glaze.
Bread maker method: add the milk, tangzhong and egg to the container. Top with the flour, salt, sugar, yeast, spices, orange zest and skimmed milk powder. Make sure the yeast does not touch the wet ingredients. Select the dough setting and add the butter when a soft dough has formed – after several minutes of kneading. The bread machine will mix the dough and do the first round of proving. Proceed with step 5 of method above.