Two types of banana go into making banana beer, the igikashi (recognisable by its harsh taste) and igisahira, which has a more neutral taste. The proportions are 1/3 of harsh-tasting to 2/3 of the other variety to ensure a balanced flavour.
You start by digging a hole, like a kind of home-made ripening gallery, big enough to pile up 5 or 6 bunches of bananas picked while still green. Make a fire from dried banana tree leaves inside the hole and line the hole with fresh banana tree leaves to stop the bunches from touching the earth. Place the bunches in the hole and cover them with more leaves and rhizomes (banana tree trunks) to hold the gallery up and keep it hidden.
4 to 6 days later, check the colour of the bananas which should be yellow, hence ripened. Peel the bananas and place them inside a hollowed canoe-shaped tree trunk. Then knead and churn them with bundles of certain very stiff grasses (called ishinge, or needles) in order to extract the juice. The first banana juice, called umutobé, can be served to women and children. You should be able to fill three to four 10 litre jugs of it.
To obtain fermentation, sprinkle each jug with ground grilled sorghum that acts as yeast. Then seal the jugs using banana leaves and leave them to stand near the hearth where a small fire is kept burning for a day and a half. Then decant the beer into medium sized jugs and leave it to stand for a whole day in a cool place.
Banana juice watered down with equal
proportions of water is called urwawa beer. You can dilute the
first juice as much as you like, according to your taste. Honey
can also be added to pure fermented banana juice to make isongo
country : Burundi
course : beverage
source : Cuisines dAfrique / A. Villers (translation at http://www.revuenoire.com/anglais/S23-4.html#Bière de bananes)