Mämmi's official name in English is: "Finnish Easter dish made of ryemeal and malted", or "Rye pudding". In Swedish it's "Memma" and in German "die Malzspeise". In Finland there are many place-names beginning with the word "Mämmi": Mämmenkoski, Mämmensalmi and Mämmensilta. In Äänekoski is also a house called "Mämmen talo" from the year 1552.
Mämmi is known to exist from the early Middle Ages, and it was specially eaten on Good Friday. Mämmi is an old Catholic lent's food, that "survived" even the reformation. Mämmi was eaten with or without bread and there wasn't anything else to eat during Good Friday. Gradually mämmi became an Easter dish, a feast, that was served to everybody who came to the house during Easter. The process of making mämmi started on Holy Thursday and it was served on Good Friday. The oldest written instruction on how to make mämmi, is from the year 1751.
Nowadays mämmi is made by using 1/3 malt and 2/3 ryemeal. The most important part of making mämmi is the temperature of water, about 60C. It is vital that the water isn't too hot and that the mixture doesn't cool down during the sweetening.
Mämmi has many other Finnish names: imellysmämmi, perunamämmi, perunaplössi, perunaprötti, plössi, prötti and tömppämämmi.
The Finns eat mostly the mämmi named "Kymppi-mämmi", made by Raisio.