In a large mixing bowl, combine the raisins, dates, candied fruits and nuts. Mix in approximately 1 cup of the flour.
Cream the butter in the bowl of a mixer, then add the brown sugar and continue mixing until it is light and fluffy. Gradually add the eggs. Alternately add the remaining flour and milk. Finally, add the baking powder, vanilla and salt. Beat another minute until the batter is creamy and smooth. Fold it into the fruit and nut mixture.
Prepare your pan by greasing, covering with brown paper and then greasing again. Pour in the batter and bake at 275° for 2 to 2 1/2 hours. (If you use dark metal pans, reduce the oven temperature to 250°.)
If you make smaller cakes, the baking time will be reduced accordingly. Make sure the cakes don't get too brown. They should be a nice golden color.