Several years ago NHK broadcast an exhaustive special on natto, containing more than you ever cared to know about that much-maligned sticky, stinky dish of fermented soybeans. One of the exciting pieces of information that NHK's crack investigative journalism revealed was the number of times required to stir natto to a frothy, snotty perfection.

The magic number? 424. Any more agitation and the beans become overworked and loose their stringiness; any less and the right amount of air will not be incorporated — air needed to create just the optimal amount of foam.

Whatever the number of stirs, true connoisseurs of natto have a specific regime when preparing to eat the little beans. A routine that will often be too much for those not yet initiated into nattohood.

Natto — soybeans soaked, steamed and then left to ferment with the bacteria Bacillus natto, a mold found naturally in straw — has been around since the Jomon Period. Just as the Egyptians and Central Asians accidentally discovered beer and cheese, natto was surely the unintended product of wrapping still-warm beans in woven-straw food pouches and forgetting about them. Whether this food was brought over from China or discovered independently in early Japan is unknown. That one day, some guy who was too hungry to care ate — and actually liked — the rotten beans is unquestionable.

While we know from archaeological evidence that natto has been around from early times, it was not written about until the Edo Period, when it was first identified as a health food. Since then, natto has been routinely prescribed as an antidote for the natsu bate (summer exhaustion) that strikes as the humidity increases after the rainy season.

We now know that enzymes in the fermented beans help lower cholesterol and stimulate the circulation, reducing the risk of blood clots and other heart problems. Along with the obvious protein, natto is also rich in essential B vitamins, including B12 — vitamins that are often missing from a vegetarian diet.

As a crop, soy makes for good agriculture as well. Soy is a legume, which means it can fix its own nitrogen and thrive in almost barren fields, improving the soil at the same time.

If a little knowledge about the benefits of natto is not enough to convert you, then maybe a little logic will.

First the smell. While it can be quite alarming at first, smell essentially just takes getting used to. There are challenging smells in most cuisines. Westerners needn't go further than some of the stinky rind-washed cheeses, or one of the really good Sauvignon Blancs that have a trace aroma of cat urine. It may take a dozen attempts, but you can get past the smell hurdle.

Next is the stickiness. Japanese cuisine has several examples of what is labeled tororo. Grating several kinds of wild tubers (yama imo) gets you the classic example of this gloopy concept. There is really no equivalent in Western cuisine. While Westerners use okra as a vegetable, they do everything in their power to minimize the slime — the precise reason the Japanese love to add it to natto — and would never prepare it raw.

For a first-timer, natto might be best eaten in a sushi roll — a preparation that reduces the slime factor and controls the aroma somewhat. Many people will only eat natto after it has been cooked — in miso soup or even in tempura.

But if you never do get it, don't worry, you're not alone. A large number of Japanese can't stand the stuff. Regionally, natto is eaten much more frequently in eastern Japan — Tokyo and the northeastern prefectures. In Kansai and western Japan, natto is absent from many refrigerators.

Natto is widely available in Japan and very inexpensive — less than 100 yen for a serving. However, it is not hard to make, and you may even experiment with different kinds of soybeans for variety.

First, you must sort and wash the beans, checking to see that there are no stones. Next, soak the beans in a good amount of water overnight. Drain the beans and cook (a pressure-cooker works well) until soft but not falling apart.

Drain the cooked beans, and while still warm incorporate either one package of good store-bought natto or a packet of the natto bacillus, available at do-it-yourself stores like Tokyu Hands. Next, keep the beans at around 40 degrees for eight hours. After this, refrigerate and let mature for several days to several weeks before eating. Keep a small amount of the beans to use as a starter next time.

Eating natto

There are many ways to prepare natto. The following is the most typical recipe, but some people add diced yama imo, chopped okra or even sashimi. Some young kids substitute mayonnaise for the raw egg yolk. You can also experiment with shiso, sesame seeds and umeboshi.

1 package store-bought natto or
50 grams homemade beans
1 tablespoon dashi
1 teaspoon mustard
1 raw egg yolk
a few drops usukuchi shoyu (light soy sauce)
finely chopped scallions
julienned nori seaweed (hari nori)

1) In a medium bowl whip the natto with a pair of wooden chopsticks until very sticky.

2) Add the dashi, mustard and a few drops of shoyu and whip again.

3) Add the raw egg yolk and continue to whip to a froth.

4) Finally add the scallions and nori, combine and serve over hot rice.