Khai Phaen (Fried Mekong River Weed Sheets)

Name: Khai Phaen (Fried Mekong River Weed Sheets)
Prep time: 50 min
Cook time: 5 min
Total time: 55 min
Yield: 4 servings
Cuisine: Lao
Ingredients: 400 g khai; 400 g green laver; 4 cloves garlic; 1 tomato; 4 tbsp sesame seeds; 10 g ginger or galangal; 1 tsp salt; 500 ml oil for frying; 4 tbsp jaew bong

The Lao drinking snack in which freshwater algae lifted out of the Mekong is spread thin with seasonings, dried into sheets, and then fried for a few seconds. The pages here that call for nori all buy it, and not one of them explains how a sheet of algae becomes a sheet. The answer is the same as paper: lay wet fibres out thin and they bond to each other as the water leaves. No paste and no starch go into it. The drying is the gluing.

Ingredients

4servings

The dried sheets (4-6)
khai · filamentous freshwater algae from the Mekong; see the tips400 g
green laver · if khai is not available; it has to be a filamentous green alga400 g
garlic · sliced very thin4 cloves
tomato · deseeded and sliced thin1
sesame seeds4 tbsp
ginger or galangal · shredded fine10 g
salt1 tsp
To fry and serve
oil for frying · something neutral500 ml
jaew bong · Lao chilli paste; gochujang loosened with lime juice will do4 tbsp

Steps

Put the algae in a big bowl and rinse it several times, changing the water each time. Getting the sand and grit out is most of the work in this dish, and whatever grit is left stays in the sheet for good.
⏲ 20 min
Shake it out without wringing it and chop it coarsely. Very long filaments bunch up as you spread them and the thickness comes out uneven.
⏲ 5 min
Mix in the garlic, tomato, sesame, ginger and salt with your hands. The seasoning goes in now — not sprinkled onto a dry sheet but embedded in it, which is what makes this khai phaen rather than nori.
⏲ 5 min
Spread it on a bamboo frame or fine mesh, thin and even, about 2mm. Pushing it to an even thickness with your fingers is the only real skill here: thick patches stay leathery and thin ones tear.
⏲ 15 min
Dry it in the sun for a day or two. It is ready when a sheet snaps as you pick it up. If it folds instead, there is still water in it.
Heat the oil to 180°C and put the sheets in one at a time. Three to five seconds and they puff and darken. Left longer they burn almost instantly.
⏲ 5 sec
Drain on kitchen paper and serve with jaew bong. They take up moisture from the air as they cool, so they are eaten where they are fried.
⏲ 2 min

Tips & Variations

Variations

Without khai: Mekong khai cannot be bought outside Laos. Any filamentous green alga works on the same principle, and green laver is the closest substitute. Sea lettuce will do, and so will nori soaked and blitzed back to a pulp. What matters is that it is filamentous rather than leafy, because it is the tangling of filaments that makes the sheet.
Seasonings: garlic and sesame are the constant; tomato, galangal, lemongrass and spring onion all turn up. In Luang Prabang it is served with jaew bong, the chilli paste made with water buffalo skin.
Undried khai: it also goes straight into soups and salads. Making it into sheets is a way of keeping it as much as a way of eating it.
Its relation to nori: this dish's own ko.wikipedia article gives 김 — the laver in gimbap — as its "see also". Same principle, and the split is salt water against fresh.

Tips

How a sheet becomes a sheet. Every page here that calls for nori buys it — gimbap, onigiri, spam musubi among them. The answer is papermaking. Lay wet fibres out thin and, as the water leaves, their surfaces come together and bond to each other. No paste and no starch are added: the drying is the gluing. Which is why there is no skill in this beyond spreading it evenly.
The seasoning is inside the sheet. Nori is brushed with oil and salt after it is dried. Khai phaen is mixed while wet, so the sesame and garlic become part of the sheet and do not come off in the oil. In the photograph the seeds are embedded rather than sitting on top, and that is why.
It is the opposite of bugak. Bugak paints a cooked glutinous rice paste onto kelp and dries that. As that page says, kelp put straight into oil "curls and burns", and what fries is the film rather than the kelp. Khai phaen has no paste at all: it is a thin fibre sheet rather than a thick frond, so it puffs and crisps by itself in seconds.
Three to five seconds. There is almost no water in a dried sheet, so what little is left leaves the moment it hits the oil. The timings in deep frying do not apply here; one sheet at a time and straight back out is the only way to do it.
The grit is everything. Algae lifted out of a river always carries sand, and skimping on the rinses is something you discover with your teeth. Five changes of water is a minimum.
Put it beside laap and nam khao and you can see how Lao cooking makes something crisp. Laap toasts raw grains to a powder, nam khao packs cooked rice into balls and fries and crushes them, and khai phaen dries river weed into sheets. All three manufacture the crisp separately and add it at the end.
Keeping it: undried sheets keep for months in an airtight box. Fried, they are for that day (serving temperature).