Just one vendor at the justifiably popular night market on Wichayanon Road, which runs between Chiang Mai's Don Lamyai and Warorot markets, was selling these nuts when we were there last month. I'd never seen them before. Nor, judging from the quizzical looks and queries cast at the woman dishing them up (10 baht for the small dish on the left, above), had most locals.
These are cha bok, a.k.a. krabok, muen, mak lai, and etc, technically not nuts but the seeds from the pit of a sour fruit with the curious name of barking deer's mango (Irvingia malayana). Cha bok are eaten in Cambodia and, I'd wager, other Southeast Asian countries as well. I suspect that they're highly seasonal (we'd never been in Chiang Mai this time of the year). The bitter, astringent shell is peeled off before eating. The 'nut' is soft, smooth, and slightly oily, and tastes a bit like a peanut crossed with a macadamia nut.
Suspecting that cha bok are a bit of a rarity, we brought a bag home for Wan. She was thrilled; she ate them as a child but hasn't seen them recently around her village in Buriram (in Thailand's northeastern Isan region) because, she says, is barking deer's mango trees have been chopped down for their exceptionally hard wood.
Cows, Wan told us, love the fruits that hide the cha bok:
When we took the cows out and leave them for the day they eat up all the fruits on the ground. We like to eat the fruits, it's sour and nice with nam prik. But we don't get to eat that many because the cows eat them all.
Then we bring the cows back to the village at night and put them into a pen underneath the houses. In the morning there's cow poop, with so many fruits in it. Around the village too. We let the poop dry [it's the hot, dry season, so this is a matter of hours], then we take the mango and wash them and peel off the fruit. We take the seed and smash it with a rock or a hammer. Inside is the cha bok.
Water buffalo? No. They don't like the mango at all. They just eat grass.
Given this story it's not too far-fetched to imagine that the barking deer's mango is so-named because it actually is a favorite food of the muntjack or barking deer, which is native to Southeast Asia. But who knows.
After dry-frying the cha bok in her wok Wan offered us a taste. Lovely - very oily and aromatic, something like a macadamia nut dipped in tahini. Wish we'd carried back more.