Dissolve the yeast in 1/2 cup warm milk and stir in 1/2 cup flour. Let rise 20 minutes.
Combine 1/2 cup flour with remaining hot milk. Add salt and knead until dough is elastic. Add yeast and mix well. Let rise 1 hour.
In a bowl, whisk 5 egg yolks and 1 egg white with the sugar and vanilla until mixture is pale.
When dough has risen, add egg yolk mixture, melted butter, orange juice and rum. Toss the raisins and candied fruit with a little flour and add to the dough. Add the remaining flour and knead well.
Form the dough into a ball, place in a clean bowl, cover with plastic wrap and let rise 2 hours.
Divide the dough between your molds or coffee cans so that each mold is 1/3 full. Let rise another 1 1/2 hours. Meanwhile, preheat oven to 180 degrees C.
Bake 35-45 minutes. Let cool then remove from molds.
Make the icing: over a warm water bath, beat remaining 4 egg whites with icing sugar for 5 minutes. Remove from heat and whisk another 5-7 minutes to make a smooth icing.