Amish friendship bread is a type of bread or cake made from a sourdough starter that is often shared in a manner similar to a chain letter. The starter is a substitute for baking yeast and can be used to make many kinds of yeast-based breads, shared with friends, or frozen for future use. The sweet, cake-like Amish cinnamon bread is a common bread that is made from this starter; it is a simple, stirred quick bread that includes a substantial amount of sugar and vegetable oil, with a mild cinnamon flavor. It has characteristics of both pound cake and coffee cake. The flavor of the finished product can be altered by cinnamon being omitted.
A common recipe using this starter suggests using one cup (240 ml) of it to make bread, keeping one cup to start a new cycle, and giving the remaining three cups to friends. The process of sharing the starter makes it somewhat like a chain letter. One cup of starter makes one standard loaf of bread.
The tradition of "passing on" the culture to a friend is very similar to the German traditional bread known as Herman cake or Herman friendship cake. Given the frequent cultural exchange between the Amish, Pennsylvania Dutch, and European German populations, it is very likely there is a common cultural root for these dishes.