Makes about 30 rusks.
You can substitute sourdough power with 120g fresh sourdough, or regular brewer's yeast.
You can also replace the flours I used with equal weight of those you prefer; keep in mind that if you increase the percentage of whole grain flours (in this case I've used it to 50%), you will get a more compact bread and therefore less light rusks.
I used brown sugar as I never use white sugar, because it's unhealthy and nutritiously poor; in this recipe it also gives a unique flavor, along with the spices and dried fruit so I suggest not to replace it.