In a bowl, combine the sultanas, currants, candied lemon and orange peel, chopped almonds and rum. Let stand overnight.
In a mixing bowl, combine 750g of the flour, crumbled yeast and warm milk. Add the butter and mix into a smooth dough, adding more flour as necessary. Let rise in a warm place, covered, for 20 minutes.
Now add the fruit soaked in rum, kneading it in so it is distributed evenly throughout the dough. Cover and let rise again for 30 minutes. Knead again.
Form into an oval loaf, using a little flour to prevent the dough from sticking. Place on a greased baking tray and, using a rolling pin, make a long indentation lengthways across the top of the stollen to make a 'trench'. Let rest for 15 minutes.
Meanwhile, preheat the oven to 200 C / Gas 6. Bake for 20 minutes at 200 C, then lower the temperature to 180 C / Gas 4 and bake for another 70 minutes. If the stollen browns too much, cover with parchment.
Immediately after baking, brush the 'trench' with melted butter and sprinkle liberally with icing sugar.