Amish Friendship Bread is a type of 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 quickbread 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.
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 two 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 recipe for Amish Cinnamon Bread may have first been posted to the internet in 1990, but the recipe itself is is several decades old.
It is not necessary to wait the canonical ten days before using one cup of starter: a cup of starter can be used as a yeast substitute at any point. However, using starter on earlier days will result in a smaller quantity of starter at the end of the cycle. To avoid running out of starter, it is normal to feed the starter (add milk, sugar, and flour) before removing a cup for use, and most recipes assume that starter is always fed immediately before being removed. A five-day baking cycle feeds the starter every fifth day and uses the resulting mixture on that day to bake one or two loaves of bread (one cup per loaf). The remaining starter is reserved to begin the next five-day fermentation cycle.
Despite common instructions to the contrary, the starter can be frozen for later use, and the cycle begun anew after thawing. The cycle can also be slowed to about half the normal fermentation rate by refrigerating the starter instead of allowing it to ferment at room temperature. Refrigeration is usually recommended if a few days' delay is desired.