Traditionally the milk was fermented in an igisabo, a gourd vessel that is also rocked back and forth to churn butter.
Raw milk ferments naturally over a day or so into a tangy, thick drink somewhere between yogurt and buttermilk, served chilled with honey or sugar stirred in on request. Milk bars — simple rooms furnished with stools and a hand-lettered menu — serve it as the default order in Nyagatare, at the heart of Rwanda's cattle country.