The gourd, called a sotet, is rubbed inside with burning sticks, often from African senna, leaving a soot lining that flavors the milk and helps preserve it.
Fresh milk is poured into a smoke-blackened calabash gourd and left to ferment for a day or more, taking on a smoky, tangy flavor from the charred lining. It's served in markets and homes across the Rift Valley in cups or bowls, often alongside ugali.