The beans get their typical herb-burnt flavour due to the butter roasting like in the Kun-Keen coffee roasting shop in Georgetown.
The process originates from the island of Hainan in China.
and has been introduced to make lower quality beans such as cheap Robusta from Indonesia drinkable.
In the oldest and most prestigious roasting, sugar is first caramelised, then the beans are roasted at 600 °C for 45 min., together with butter and some sesame.
Out comes blackish, bubbling liquid resembling lava, which gets cooled, chopped into brick-sized chunks and run through 3 different mills.