Called Hverabrauð in Icelandic, this volcanic rye bread is made using one of the most unconventional baking methods. The bread is put in a pan which is then buried in the ground next to hot water springs. Iceland is a country with a lot of tectonic activity, 30 active volcanoes, and countless hot springs. The heat in the ground gives the bread a 24-hour long bake. Click here to watch a short documentary about the process.
Now, most of us don't have hot springs nearby, but you can mimic these environmental conditions by slow-cooking the dough in the oven overnight. In this case, the bread is called Rúgbrauð.