“Roasted Sweet Potato,” Enchanting Melodies and Memories of Nectar - An Essay on Seasonal Traditions

Why is it that we become so restless whenever we hear that voice?

Resonating from around the distant corner,
“Ishi-yaki-imo, oimo.
Delicious, delicious, it’s sweet potato~”
the voice calls out.

That is less of a sales pitch and more like an intangible cultural heritage announcing the arrival of winter.
Do you clutch your wallet and dash out the front door, or do you burrow deeper into your kotatsu, thinking, “It’s still far away”?
That few seconds of hesitation might just be the proper way to welcome winter in Japan.

In the first place, the existence of the roasted sweet potato vendor was born from the mysterious boundaries of Edo-period towns.
It is said that the roots of roasted sweet potatoes lie in the side businesses started by the “kido-ban” (gatekeepers) who guarded the town boundaries of Edo, right at the eaves of their guardhouses.

The kido-ban were like the security guards of today.
They sat at the borders between neighborhoods, keeping watch at night, and roasted potatoes using their leftover fire.
In other words, roasted sweet potatoes were a share of good fortune that the “men who guarded the boundaries” passed on to the townspeople while keeping themselves warm.

Roasted sweet potatoes back then were not stone-roasted like they are today, but were mainly steamed in large cauldrons.
It is said that their signs featured a clever pun typical of the Edo spirit: “Better than chestnuts (kuri), thirteen ri (jusan-ri).”
This plays on the fact that the distance from Edo to Kawagoe was about thirteen ri, and thinking that this calculated humor forms the foundation of the modern “Ishi-yaki-imo” melody makes me feel strangely delighted.

The shape of the stalls has also undergone many transformations to match the times.
While large carts and handcarts were once the norm, light trucks and minivans took over that role from the middle of the Showa era.

That unique rhythm of “Ishi-yaki-imo, oimo!” actually has a physical necessity.
The sales call is drawn out to calculate the “grace period” for customers to come out from their homes, matching the walking speed or the slow movement of the vehicle.
That melody is, so to speak, a communication protocol dedicated to the streets that takes the Doppler effect into account.
Although recorded tapes have become the norm recently, the reason that melancholic tone is still preserved must be because the Japanese DNA craves that frequency.

The potatoes once roasted by the “guardians of the boundaries,” the kido-ban, have moved in modern times to the “modern boundary line” of supermarket entrances.
Electric roasted sweet potato machines placed at the entrance of supermarkets.
Is there anyone in this world who can resist the violently sweet aroma drifting from there?

Perhaps we are now seeking at supermarket entrances the salvation we once found in the gods of the streets.
The sight of a potato glowing golden is truly that divine.

Now, trying to recreate such “sacred potatoes” at home is a ritual that even carries a sense of guilt.
However, if you have physics on your side, it is possible to create that golden universe in your home kitchen.

The secret is, above all, not to rush the potato.
For the enzyme called beta-amylase in sweet potatoes to convert starch into maltose, the key is how long you can maintain the temperature range of 50 to 60 degrees Celsius—a kind of “lukewarm hell.”

First, wash the potatoes well and soak them in concentrated salt water for about an hour.
This makes the skin less likely to break and brings out the sweetness.

Next, wrap them like mummies in wet newspaper (or paper towels), and then pack them securely with aluminum foil over that.

All that’s left is to bake them in a toaster oven at 190 degrees for 60 minutes, and once they are cooked, leave them inside for another 30 minutes. Yes, a total of 90 minutes.
The act of “waiting,” which modern people are worst at, is the ultimate seasoning.

When you take it out of the toaster oven and break it open with your hands, it doesn't make a 'snap,' but rather a 'squish' sound.
What overflows from within is the scent of nectar, released along with the steam.
It is no longer just a vegetable, but a supreme sweet that the earth has spent time brewing.

As I write this, I find myself missing that voice once again.
Even if the street stalls have disappeared and settled into their fixed spots at the supermarket, the image of the bare lightbulb glowing in the dark and the smell of that smoke remain etched in our hearts.

Perhaps tonight, somewhere, that 'ishi-yaki-imo' voice might quietly echo.
If you happen to hear it, try rushing outside, even if you have to put your shoes on the wrong feet.
For what awaits you there is a gift from beyond the boundary, the hottest and sweetest tradition that has continued since the Edo period.

Why not start preparing to slowly roast the largest sweet potato you have at home next?