Siggi Rafn Hilmarsson lives in Laugarvatn, Iceland, and has been making lava bread for years, following in the tradition of his elders. The bread is made using rye and wheat flour, sugar (or sometimes honey), local milk, and he says to also put some love in it. The dough is thin in texture when mixed up, almost more of a cake batter. The mixture is then poured into a heavy greased pot, covered in wax paper, then wrapped in plastic wrap before the lid is placed on.
The lidded pot is then placed the heat of the natural volcanic sand and stone beaches near one of the many naturally-occurring hot springs- a common geographical feature of Iceland. The pot is placed in the ground and then covered with more of the hot stones and sand and then marked with a special stone on top of the mound. The bread is left to bake in this natural oven for 24 hours.
After the allotted time a shovel is used to dig the pan up. The temperature of the sand is around 100˚F, so this type of baking is not unlike making Boston brown bread in a pot of boiling water.
When the bread is done it is often served with fish or with boiled eggs (boiled in the water of the hot springs). However, Hilmarsson says that guests from outside Iceland say the bread reminds them of gingerbread a little bit. See this incredible tradition in action in the video below.