Add the dried yeast to the warm milk and whisk together. Place the cup in a warm place for 15 minutes or until the mixture has become frothy.
In a large bowl, sift together the plain flour, nutmeg, cinnamon, salt and caster sugar.
Add the butter and rub together until the mixture resembles fine breadcrumbs.
Pour in the milk/yeast mixture, the egg and the warm water. Sprinkle over the sultanas.
Stir together until the mixture forms a round dough ball.
Grease a bowl with cooking spray and place the dough ball into the bowl.
Cover with a tea towel and leave in a warm spot to rise for 30 minutes or until doubled in size (see notes).
Preheat oven to 200 degrees celsius (fan-forced).
On a lightly floured board, place the dough and knead for 5 minutes.
Divide the dough into 12 equal sized portions and roll each portion into a ball.
Place the balls (1cm apart) in a greased 20cm X 30cm baking tin. Set aside for a further 15 minutes to prove.
Make the piping by sifting the flour into a bowl and adding enough water to make a paste.
Pipe the crosses onto the buns using a piping bag or a glad bag with the end snipped off.
Bake in the oven for 15 minutes or until the buns sound hollow when tapped.
To make the glaze, place the water and sugar into a microwave safe bowl and heat for 30 seconds. Mix until the sugar dissolves.
Brush the tops of the buns with the glaze.
Place the buns onto a wire rack to cool.