Boil potatoes in a large pot until tender, mash well with a fork. Set aside.
In a medium bowl mix together 1/4 cup of the water, molasses and dry yeast. Let sit for 5 minutes for the yeast to activate.
In the bowl of your stand mixer stir together flour and salt. Combine the mashed potato, the remaining 1/2 cup of water and the olive oil in a medium bowl and add it to the flour mixture.
Finally add in yeast mixture and start mixing until a dough forms, around 8 minutes. Incorporate the mix of walnuts, hazelnuts and raisins after 4 minutes of kneading time. You might need to add extra flour so do it one tablespoon at a time until the dough is smooth, it doesn't stick too much to your hands and it's pliable.
Shape dough into a ball.
Place the dough in a large bowl, cover with plastic wrap and let rise for 90 minutes.
Flatten the dough a bit to force out any excess gas. Divide it into 2 equal portions and shape each one into an approximately 8-inch (20 cm) loaf.
Place the loaves on a lightly floured baking sheet and sprinkle some flour on the tops. Loosely cover with plastic wrap and let rise for 30 minutes, until puffed.
Preheat oven to 400ºF (200ºC).
Remove the plastic wrap from the loaves and bake for 25-30 minutes, or until the loaves are deep brown and sound hollow when the bottoms are tapped.
Let cool on a wire rack.