Zwieback are slices of bread baked in an oven to make them dry and crispy.
They are often made from bread that is slightly sweetened, or has egg in it. Some variations have mashed potato in the bread. Usually the bread is purpose-made from a recipe intended for it to be made into Zwieback. The baked bread slices will be light.
Zwieback is often given to babies to teeth on. Nabisco and Gerbers both make (as of 2004) boxes of Zwieback aimed at babies.
Children will also eat them broken up into a bowl with cream and sugar poured over them.
Zwieback is very similar to Dutch rusks.
Zwieback is often crushed, with a rolling pin or in a food processor to make crumbs, which can be used as you would Graham cracker crumbs to make a pie crust. “Cheese Torte”, a classic German-style cheese cake, has a crust made from Zwieback crumbs. They can also be broken up into a soup, as you would a cracker.
1 standard package of Zwieback = 6 oz = 170g
Zwieback appears on supply lists for troops in the American Civil War. In New York, the Anger Bakery (now a part of Nabisco), began selling Zwieback in the 1880s.
The word should technically be actually “Zweibach”, but Zwieback is indeed the name for it. “Zwieback” comes from what the Germans call “Platt Deutsch”. It means “twice baked”.