Sylvia at Adventures of an Orthodox Mom describes how to bake prosphora (bread used for Orthodox liturgies) as it is made at Mount Athos and the Athonite monasteries.
We use something called "prozimi" instead of yeast to make the bread rise. Prozimi itself is a miracle. On either September 14 (Exaltation of the Precious Cross) or on Holy Friday a bowl containing only water and flour is taken into the altar during the Gospel reading. The priest then blesses it. Afterwards our Gerondissa takes it into the kitchen and places it in the oven (the oven is not on) and leaves it there overnight. The next morning the bowl is overflowing with this "yeast". It is then separated and refrigerated in airtight containers and is used each time prosphoro is made. Every time you make a new batch of dough you tear a small piece off and set aside for next time.Check out the full recipe, complete with pictures. Almost reminds me of my Eucharistic bread recipe adventures from a few years ago.
(H/T Byzantine, Texas)