In a small bowl or jug, combine the sugar, yeast, warm milk and 100ml of warm water. Set aside for approximately 5 minutes or until the mixture is foamy. Whisk the egg into the mixture.
In a large bowl, mix together the flour and mixed spice. Using your fingertips, rub the butter into the flour mixture until it resembles breadcrumbs. Add the fruit and stir. Make a well in the centre of the flour mixture and pour the yeast mixture in. Stir to create the dough. Turn the mixture out onto a lightly floured surface and knead for 10 minutes or until smooth.
Place the dough in a lightly greased bowl. Cover the bowl with plastic wrap and place in a warm draught-free place for an hour or until the dough doubles in size.
Grease a Large Q Ware Frying Pan with butter. Remove the dough from the bowl and turn onto a lightly floured surface. Knead again until the dough returns to the original size. Divide the dough into 12 portions and roll into balls. Place side by side in the pan. Cover with lightly greased plastic wrap and set aside in a warm, draught-free place for 30 minutes or until the dough has doubled in size.
Prepare the barbecue for indirect cooking over medium-low heat (close to 180°C as possible). If using a Weber Q barbecue, set up your barbecue with a convection tray and trivet.
To make the flour paste, combine 1/4 cup (60ml) cold water, flour and sugar in a bowl. Spoon the mixture into a snap-lock bag and snip off 1 corner. Pipe the crosses onto the buns.
Bake the hot cross buns over indirect medium-low heat, with the lid closed, until cooked through and the buns are golden, about 20 to 25 minutes.
While the buns are cooking, make the glaze. Combine the sugar, gelatin and 1 tablespoon of boiling water in a bowl, stirring until the sugar and gelatin have dissolved.
Once the buns are cooked, turn out onto a wire rack. Using a pastry brush, brush the buns with the glaze.
Best enjoyed warm and served with butter.