In a large bowl, dissolve the yeast in half of the water, then add the two flours, the acacia honey and the grated orange peel. Knead, by hand or with the hook of a stand mixer, adding more water when needed.
Knead for about 5 minutes, then add the salt and a few drops of water and continue to knead until the dough has absorbed all the salt and the water.
When the dough starts to wrap itself around the hook of the mixer and becomes elastic, add the soft butter cut into small pieces. Keep on kneading until all the butter is incorporated, obtaining a smooth and elastic dough. Squeeze the raisins and add them into the dough, kneading just enough to distribute them evenly.
Let the dough rest for half an hour, covered with a towel and grease a 22-25 cm long cake mold.
Divide the dough into three equal parts and shape them into three balls, closing them tightly onto themselves, as shown here or here.
Place the three balls of dough inside the buttered mold, cover with cling film and let rise in a warm spot, protected from drafts, for a few hours, or until the brioche bread is doubled.
Heat the oven to 180°C and gently brush the brioche bread with a beaten egg: you will certainly need less than half of it. Sprinkle the granulated sugar over the brioche bread.
Bake for about 40 minutes, until golden brown.
Remove the brioche bread from the oven and let it cool down completely. A secret in between you and me: I can not resist this brioche when it is still warmish from the oven, with butter and honey.
It keeps for a few days wrapped in a clean kitchen towel. If it becomes a little too dry, toast it on a hot pan.