That striking color comes from Yen Ta Fo sauce, a special ingredient made mainly from fermented red tofu.
The name "Yen Ta Fo" has Hakka Chinese roots, and while it's a popular dish among Hakka communities, the name doesn't actually mean "fermented tofu." There's some debate about the name's origin, but it likely evolved from how Teochew Chinese speakers pronounced a similar term, eventually becoming "Yen Ta Fo" as we know it.
A crucial part of Yen Ta Fo is the stuffed tofu, called "Tao Hoo Khae" in Thailand. This ingredient is also found in "Hakka-style noodles" and has a long history, tracing back over a thousand years to Hakka culinary traditions. It's a beloved food not just in China, but also in other places with large Hakka populations, like Malaysia, Singapore, Hong Kong, Taiwan, and Thailand. Malaysia even considers "Ngiong Tao Fu" (a similar dish) one of its national culinary treasures.
Beyond the signature red broth, Yen Ta Fo usually features crispy fried tofu, little pieces of Chinese crullers (Patongo), crunchy squid, cubes of congealed pig's blood, and morning glory. You might also find crispy wontons, sliced fish, or fish balls in some versions, especially in Rayong province.
Over time, Yen Ta Fo has branched out into different versions, like the classic, spicy tom yum, and seafood options, to cater to various tastes. While we don't know exactly when Yen Ta Fo was first created, it's likely that the strong flavors of Thai cuisine influenced the dish.
Traditional Chinese food tends to be milder, so the addition of fermented tofu probably gave rise to the distinct taste and the name "Yen Ta Fo" that we enjoy today.