Whisk the flours together in a large mixing bowl.
Add in the unsalted butter then rub together between your fingertips until the mixture resembles breadcrumbs.
Stir in the sugar, yeast, salt, cinnamon, mixed spice, nutmeg and the lemon and orange zest until well combined.
Beat the eggs in a medium sized mixing bowl and gently pour in the warmed milk in a thin stream, whisking all the time until combined.
Pour the liquid mixture into the middle of the flour mixture.
Use a wooden spoon to mix at first, then as the dough begins to come together use your hands.
Knead gently until the dough is almost smooth but still has some loose flour then add the dried fruit.
Continue to knead the dough so all the fruit is evenly incorporated then turn into a smooth ball. It will still be a little sticky.
Leave the dough ball in the mixing bowl and cover loosely with a tea towel. Rest in a warm place for 1 hour.
Pre-heat the oven to 180°C/160°C fan assisted/gas mark 4
Remove the tea towel then tear off 100g pieces of the dough. Roll into 10 balls and place evenly spread out on a large baking sheet.
Set the baking tray aside whilst you prepare the crosses.
Mix the oat flour and sweet rice flour together in a small bowl then add the water. Stir together until it forms a paste.
Spoon the flour paste into a small piping bag, or food bag with tip snipped off.
Pipe crosses onto the top of each bun.
Place the Hot Cross buns in the oven and bake for 20 minutes.
Remove the Hot Cross Buns from the oven. Place the buns on a cooling rack and set aside whilst you prepare the glaze.
Heat water and sugar in a small saucepan until bubbling and the sugar has dissolved.
Use a pastry brush to brush the glaze over each Hot Cross Bun.
Serve warm or cooled, split in half with a slick of salted butter.