Add the yeast and sugar to the lukewarm milk. Leave for the yeast to activate (approx. 10 min). You should see some small bubbles forming on the surface.
Mix the yeast-milk mixture, flour, butter, sugar and salt. Knead with a dough hook, using a hand or stand mixer for 5 minutes. Leave the dough to rest for a further 5 minutes. Then knead the dough again for another 5 minutes. (The total kneading time should be 10 minutes in total).
Pour boiling water over the raisins and currents, then drain them well and add them to the dough. Knead again for about one minute (not too vigorously as you do not want the raisins to burst.
Cover the bowl with a kitchen towel and leave to rest for at least 1 hour.
After this time the dough should have roughly doubled in size. Remove from the bowl and place into a greased loaf form.
Brush the top with a little milk and bake it at 180 °C /350 °F degrees for 45-50 minutes.