It looks just slightly bigger than a chocolate bar, and about as thick. It has three thin layers, one bright yellow sandwiched between two whites, like a rectangular slice of hard boiled egg. The humble appearance of bánh khảo, like so many other Vietnamese old school treats, masks tremendous creativity and skill of the country’s villagers.
And so little is known about it. Some just say it came from the Chinese immigrants, others believe it’s a special fare of the Tày, an ethnic group in the second-farthest-north-border province Cao Bằng, where Chinese influence seeps through the forests and mutates with a mountainous feel. All we know is when you go to Cao Bằng, you get a bar of “pẻng cao” (bánh khảo) for 1000VND (less than 6 US cents), whose middle layer can either be sweet with peanuts and honey, or savory with sliced fatty pork.
The savory kind is a staple to the Tày people. The flour from roasted sticky rice grains, let sit overnight, mixed with sugar and pressed into a thin sheet, somehow can stay good for a whole month. Its light weight makes a good dry snack to pack for long trips in the mountains. But when it goes south to the Red River Delta and all the way down to Saigon, pork slices and peanuts give way to the all time popular mung bean paste. Bánh khảo looses savoriness and gains homogeneity. It becomes bánh in nhân đậu xanh.
Chewy and grainy. Not too sweet, rather mild. To be eaten slowly between sips of tea to avoid coughing or throat irritation. That’s the nature of two layers of sandy white sticky rice flour sandwiching one of bright yellow mung bean paste, like a rectangular slice of hard boiled egg.
Dull sidenote: not the stuff you’d want to make at home with roasting and grinding and pressing, when it costs 2 bucks and a quarter at any Vietnamese sandwich shops in San Jose, Kim’s for example.