Place the raisins and currants in a bowl. Sprinkle the fruit with 3 tablespoons of the sugar and the rum, if used. Covered the bowl and let stand for 24 hours.
Stir the compressed or dry yeast into the lukewarm milk. Sift the flour and salt into a bowl and make a well in the center. Pour the yeast mixture into the well and stir a little of the surrounding flour into the liquid. Cover with a cloth and let stand in a warm place for about 30 minutes. Measure the butter and let stand at room temperature.
Sprinkle the remaining sugar, the nutmeg, ginger and grated lemon and orange rind over the flour. Mix the dry ingredients into the yeast mixture and beat in the softened, but not melted, butter. Knead the dough well on a floured board until no longer sticky. Place in a bowl, cover with a cloth and let stand in a warm place for several hours until doubled in bulk. Sprinkle the raisins and currants with the 1 tablespoon of flour and knead into the dough on a floured board with the almonds and candied peel. Shape the dough into an oval. Cover with a cloth and let rise on the board, in a warm place, for 30 minutes.
Using a rolling pin, make a deep depression lengthwise along the center of the oval and fold one half down over the other. Place the dough on a warm baking sheet lined with waxed paper or parchment paper. Once more cover the dough with a cloth and let rise for a further 30 minutes.
Bake in the center of a preheated moderately hot oven 375°F for 1 hour. Remove from the oven and, while still warm, spread liberally with the butter. Then coat thickly with the confectioners’ sugar.
NOTE: Since Christmas bread matures and improves in flavor on keeping, it is advisable to make it at least 1 month before it is required, and keep in an airtight container or wrap in aluminum foil.