Gently heat the milk until lukewarm, add the sugar and whisk until dissolved. Add the yeast and whisk in (make sure your milk is only warm, you don't want to kill the yeast).
If using dried yeast, leave for 5-10 to activate until it's nice and frothy.
In a large bowl combine the flour, cinnamon, mixed spice and salt. Rub the butter through the flour mixture until well distributed.
Stir the sultanas through the flour and then add the eggs and yeast mixture. At this point either stir to bring it together and then turn out on a board and knead it for 5 minutes, or employ your electric mixer and dough hook for 5 minutes.
Note: at this point my dough looks pretty sticky, but don't despair, this is fine, don't be tempted to add lots of extra flour.
Place the dough in a bowl and cover (I love using beeswax wrappers for this) and leave to rise for about 45 minutes in a warm place.
Preheat the oven to 180°C (or about 160°C fan-forced). Take the dough out of the bowl and knead a few times before dividing up into 12 equal pieces and then shaping them into balls.
Place the balls on a greased baking sheet (I just used a reusable baking sheet/paper) pressed lightly up against each other, cover with a tea towel and leave for a further 15 minutes to rise.
To make the cross: Combine the flour and baking powder in a small bowl and add about 3 or 4 tablespoons of water until you have a runny batter. Place in a piping bag with a narrow nozzle (or a bag with the ol' snipped corner trick) and pipe the crosses over the buns.
Bake for about 25 minutes until they are a lovely golden brown and sound hollow when tapped.
In a small saucepan heat the jam with a little water and then brush this over the hot buns to glaze before placing them on a baking rack to cool (the less water you add, the stickier the top of the buns will be).