Place the sultanas, almonds and rum in a bowl, cover and leave to soak for approx. 2 hrs.
Place the flour in a bowl and create a well in the centre. Pour the milk, sugar and yeast into the well, mix in a little of the flour to create a thin paste, leave to stand for approx. 30 mins.
Add the sugar to the flour along with all the other ingredients up to and including the nutmeg, mix. Add the milk and butter, knead to form a soft, smooth dough, cover and leave to rise for approx. 3 hrs. Knead the soaked sultanas and almonds into the dough in batches.
Divide the dough in half. Roll into two ovals approx. 3 cm thick. Shape the marzipan into two long rolls, place in the middle of the two ovals. Fold over ⅔ of the dough and place on a baking tray lined with baking paper. Cover and leave to rise for approx. 30 mins., brush with ⅓ of the butter.
Approx. 15 mins. in the centre of an oven preheated to 180°C. Remove from the oven, brush with ⅓ of the butter and return to the oven for approx. 15 mins. Remove, brush with the remainder of the butter, leave to cool on a rack. Dust the stollen with icing sugar.