Japan’s Vending Machines Are Disappearing — Here’s Why
Japan’s Vending Machines Are Disappearing — Here’s Why is a easy Japanese recipe that serves 4. 180 calories per serving. Recipe by How To Cook That on YouTube.
Prep: 5 min | Cook: 3 hrs 10 min | Total: 3 hrs 30 min
Cost: $3.15 total, $0.79 per serving
Ingredients
- 4 pieces Japanese Sweet Potatoes (medium size, about 200‑250 g each; scrubbed clean)
- 1 tablespoon Olive Oil (light coating to prevent sticking)
- 1 teaspoon Sea Salt (optional, for finishing)
Instructions
Clean and Pierce Potatoes
Rinse the sweet potatoes under cold water, scrub off any dirt, pat dry, then pierce each potato 6‑8 times with a fork to allow steam to escape during baking.
Time: PT5M
Low‑Temperature Bake
Line a baking sheet with parchment paper, drizzle the olive oil and toss the potatoes to coat lightly. Arrange them in a single layer and place in a pre‑heated oven at 120 °C for 3 hours, turning once halfway through.
Time: PT3H
Temperature: 120°C
Optional Quick Broil for Extra Crispness
Increase the oven temperature to 250 °C, broil for 5 minutes, watching closely until the skins develop a slight crisp.
Time: PT5M
Temperature: 250°C
Serve Warm
Remove the potatoes with tongs, sprinkle lightly with sea salt, and serve immediately while hot and soft inside.
Time: PT2M
Nutrition Facts
- Calories
- 180
- Protein
- 2 g
- Carbohydrates
- 40 g
- Fat
- 0 g
- Fiber
- 5 g
Dietary info: Vegan, Gluten‑Free, Vegetarian
Ingredient Substitutions
- Instead of Japanese Sweet Potatoes: Regular orange sweet potatoes, Yams
- Instead of Olive Oil: Vegetable oil, Canola oil
- Instead of Sea Salt: Kosher salt, Himalayan pink salt
Equipment Needed
- Oven
- Baking Sheet
- Parchment Paper
- Fork
- Tongs (optional)
Critical Steps — Do Not Skip
- Piercing the sweet potatoes prevents steam buildup and possible explosion.
- Baking at a low temperature for an extended time preserves the natural enzymes that convert starch to sugar, giving the characteristic sweet, date‑like flavor.
Chef Tips from the Video
- Choose sweet potatoes with a uniform size for even cooking.
- A light drizzle of honey after baking enhances the natural sweetness without overpowering it.
Troubleshooting
Potatoes are hard in the center after baking.
Increase the bake time by 15‑30 minutes or raise the temperature to 130 °C for the final hour.
Skin becomes too dry or burnt.
Cover the potatoes loosely with foil for the first 2 hours, then uncover for the final hour.
Storage
Refrigerator: Store in an airtight container for up to 4 days; reheat in a microwave or oven.
Freezer: Not recommended; texture changes when frozen.
Room temperature: Can sit at room temperature for up to 2 hours; beyond that, quality declines.
Make-Ahead Tips
- Bake the sweet potatoes a day ahead and reheat in a 180 °C oven for 10‑15 minutes.
- Cold‑stored potatoes can be sliced and microwaved for a quick snack.
Frequently Asked Questions
What is the cultural significance and history of yaki‑imo in Japanese cuisine?
Yaki‑imo, or roasted sweet potato, has been a popular street snack in Japan since the early 20th century, often sold from small stalls and vending machines. It is especially associated with autumn and winter, when the cooler weather highlights its warm, sweet flavor.
What regional variations of yaki‑imo exist within Japan?
In Hokkaido, yaki‑imo is sometimes brushed with a light soy‑sugar glaze, while in Kyushu the sweet potatoes are often smoked over charcoal for a deeper flavor. Some regions also use purple sweet potatoes for a vibrant color.
How is yaki‑imo traditionally served in Japan?
Traditionally, yaki‑imo is served hot, unpeeled, and eaten straight from the skin. Vendors often sprinkle a pinch of salt or a drizzle of honey, and it is enjoyed as a quick, handheld snack.
During which Japanese celebrations is yaki‑imo commonly enjoyed?
Yaki‑imo is a staple at autumn festivals (秋祭り) and winter street markets, where the warm, sweet aroma draws crowds. It is also a comforting snack during New Year’s visits to shrines.
What makes yaki‑imo special compared to other sweet potato preparations in Japanese cuisine?
The low‑and‑slow baking method preserves an enzyme that converts starch into natural sugars, giving yaki‑imo its distinctive caramel‑sweet, date‑like flavor and a soft, melt‑in‑the‑mouth texture that differs from typical roasted or fried sweet potatoes.
What are the most common mistakes to avoid when making low‑and‑slow baked yaki‑imo at home?
Skipping the piercings can cause the potatoes to burst, and baking at too high a temperature will destroy the sweet‑enhancing enzymes, resulting in a bland, dry interior. Keep the oven at 120 °C and turn the potatoes halfway.
Why does this yaki‑imo recipe use a low temperature of 120 °C instead of a higher roasting temperature?
A low temperature allows the natural enzymes to slowly break down starch into sugars, creating the signature sweet, sticky flavor. Higher heat would denature the enzymes and produce a less sweet, more caramelized exterior.
Can I make yaki‑imo ahead of time and how should I store it?
Yes, bake the sweet potatoes a day ahead, let them cool, then store in an airtight container in the refrigerator for up to 4 days. Reheat in a 180 °C oven for 10‑15 minutes to restore the soft interior.
What texture and appearance should I look for when my yaki‑imo is done?
The skin should be lightly crisped, the flesh soft and almost buttery, and a faint caramel sheen should be visible when sliced. A fork should slide in with little resistance.
What does the YouTube channel How To Cook That specialize in?
The YouTube channel How To Cook That, hosted by Ann Reardon, specializes in science‑based cooking tutorials, debunking food myths, and recreating popular food trends with clear, evidence‑driven explanations.
How does the YouTube channel How To Cook That's approach to Japanese snack recipes differ from other cooking channels?
How To Cook That focuses on the underlying chemistry of why Japanese snacks like yaki‑imo taste the way they do, often testing temperature and time variables, whereas many other channels simply demonstrate the final product without explaining the science.
Last updated: September 6, 2026
