Hot cross buns are traditionally eaten on Good Friday; legend has it than a bun baked on this day will never go mouldy (although I don't recommend that you try it!). They're made from a rich yeasted dough, full of spices and dried fruit to mark the end of Lent. I prefer them toasted myself, and with a faint smear of butter and jam. —londonbakes
In a large bowl, or the bowl of a stand mixer fitted with the dough hook, whisk together the flour, yeast, sugar, and salt.
In a small pan, heat together the milk and butter until the butter has melted and the milk is warm to the touch (the temperature at which yeast is activated).
Make a well in the middle of your dry ingredients and add the milk and butter mixture, followed by the egg. Bring the mixture together with a wooden spoon or your hands and then knead until smooth and elastic (about five minutes with a stand mixer; slightly longer by hand).
Place the dough in a lightly greased bowl and cover with plastic wrap. Put the bowl somewhere warm and allow the dough to rise until doubled in size, about an hour or so.
When risen, remove the dough from the bowl and lightly knead in the spices and mixed fruit until evenly distributed. Divide the dough into 12 equal portions and shape into a bun. Place the buns on a baking tray, lined with parchment paper, allowing a little space between each. Cover the buns with plastic wrap and allow to rise again for an hour or so, until they have puffed up and doubled in size.
Preheat the oven to 425° F (220° C).
When the buns have risen, make a smooth paste by mixing together the flour and a little cold water (about 1to 2 tablespoons). Pipe a cross onto each bun.
Bake for 15 to 20 minutes until golden brown. As they are just about to finish cooking, combine the sugar and boiling water and mix until the sugar has dissolved. Remove the buns from the oven when baked and brush them with the sticky syrup until they look all shiny and appetizing.
The hot cross buns are best eaten the day they are baked, but can be kept in a cool, dark place for a couple of days and revived in the oven if they get a bit stale. The baked buns also freeze nicely, so you can have a taste of Easter all year long.