Place the flour, sugar, yeast and salt in a large bowl. Add the softened butter and use your hands to rub the butter into the flour mixture to make a fine crumb. Add the milk, nutmeg, allspice and vanilla extract. Using a knife, bring the mixture together to form a soft dough.
Transfer to a generously floured work surface and knead for 6 to 7 minutes, adding more flour if necessary, until smooth and pliable. The dough will have a slightly rough appearance. If preferred, you could use an electric mixer with a dough hook to knead for 5 minutes. Shape the dough into a ball and place in a bowl. Cover with plastic wrap and leave to rise for 1 to 2 hours in a warm place, or until doubled in size.
Remove the dough to a lightly floured surface. Using your hands, flatten the dough to a large disc. Sprinkle with half the macadamias and fruit and use a rolling pin to press them into the dough. Fold the dough up and knead lightly before repeating with remaining macadamias and fruit. Lightly flour a work surface and roll the dough out to a large rectangle measuring 25cm x 45cm. Brush with melted butter and set aside.
Roll out the marzipan between 2 sheets of baking paper to form a 30cm x 15cm rectangle. Remove the top layer of baking paper and flip over onto the rolled out dough so that it sits flat in the centre. Remove the top layer of baking paper and roll up the dough lengthways from the longest side of the rectangle to form a roll. Place the roll on a lined baking tray. Cover loosely with plastic wrap and stand in a warm place for 1 hour, until puffed and slightly risen.
Preheat oven to 190°C. Remove the plastic wrap and place the dough in the oven. Reduce heat to 160°C and bake for 40-50 minutes, until the stollen is golden, cooked through in the centre and sounds hollow when tapped. It may be necessary to cover with aluminium foil during baking to prevent burning. The stollen will also be quite heavy so be careful moving it when testing for readiness.
Remove from the oven and allow to cool for 15 minutes before brushing with melted butter and dusting with icing sugar.