Add sugar and yeast to 150ml of warm water (24 to 27 degrees C), do not stir. Rest for 5 minutes, and then stir until dissolved.
Mix flour and salt in large bowl then add sultanas, raisins and/or currants and the mixed spice. Make a well in the centre of the flour mixture then pour in the yeast water, along with an additional 100ml warm water. Mix and stir to form a moist (not wet) dough, gradually adding a little more warm water if needed.
Knead dough for 10 minutes on floured surface until smooth and elastic. Place dough in a large bowl lightly brushed with oil. Cover bowl with cling film and rest in a warm place (24 to 27 degrees C) for 1 hour, until the dough has doubled in size.
Punch the dough down, and let it rest for another 10 mins.
Remove from the bowl and divide dough into 8 equal sized pieces (about 120g each). Roll each piece into a ball and flatten. Make a hole in each bagel to form a ring. Place on lightly oiled baking tray. Re-cover with cling film and rest for 10 minutes.
Preheat oven to 220 C / 200 C fan / Gas 7.
Bring a large saucepan of water to the boil over a high heat then reduce the heat bringing the water to a simmer.
Lower bagels (2 to 3 at a time) into the water. Cook for 1 minute per side, per bagel. Remove and drain for a few minutes.
Brush melted butter, syrup or honey over and sprinkle with sugar. Place bagels on two baking trays lined with baking paper.
Bake in the preheated oven for 20 minutes, until golden brown; rotate/swap over baking trays after 10 minutes to ensure even baking. Remove from the oven and cool on a wire rack before serving.
Always use fresh yeast. Always use a thermometer to monitor the temperature range; too cold and the yeast will be sleepy, too hot and the yeast will die.