Chilled Oil Udon with Yuzu Ponzu, and Microwave Hot and Sour Soup with Leftover Egg Whites

According to Ryuji, there haven't been many recipes of theirs that use ponzu. There were few ponzu brands they liked, and when they did use it, they chose "Ajipon." They describe this Kaori no Kura as a yuzu ponzu with a pronounced yuzu aroma and strong umami. Ponzu is usually a winter seasoning, but Ryuji's view is that with the aroma of yuzu, it works perfectly well in the hot months too.

Before starting to cook, Ryuji makes a toast with a yuzu sour of shochu mixed with this ponzu and soda water. Used in place of lemon juice, the yuzu really comes through and it's excellent, they say, recommending it as a mixer as well.

Ryuji says people have been telling them their recent videos are long, so this one will be kept short. There's no frying pan involved; it's just making udon, with the kind of ease of their "kyomu" (void) recipes. They also reveal that they were working until 8 a.m. the day before and are short on sleep, adding that this is a recipe you can make even in that state. On how few steps there are, Ryuji also remarks, "It's like my early recipes" and "The fastest in my recipe collection."

The sauce is mixed first and chilled in the refrigerator. Ryuji says the proportions went through a lot of trial and error, and this was the most delicious.

• Kaori no Kura Marushibori Yuzu: 1 1/2 tablespoons
• Chicken bouillon powder: 1/2 teaspoon (for umami)
• Sugar: 1/2 teaspoon (for richness)
• Salt: a pinch (optional)
• Sesame oil: 1 tablespoon
• Grated garlic: about 5 g
• Black pepper: to taste

The ponzu is delicious on its own, but since this udon is eaten cold, flavor is built up on top of it. Ryuji explains that the acidity of ponzu tastes good in summer. The salt is a personal preference, added "because I'm a drinker," and can be left out. Garlic powder can be substituted for the garlic, but grated garlic tastes better, they say. Their argument is that simple things like this are the tastiest.

The side soup is there because when you eat a lot of something cold, you start to want something warm to drink. Only the yolk is used for the udon, so the leftover egg white goes into this soup.

Tear about 30 g of oyster mushrooms into a heatproof cup. Any kind of mushroom is fine, and something like green onion works too, Ryuji says. For the water, they start to say "about 200 cc" before correcting it to 180 cc. Add 1/2 teaspoon of chicken bouillon powder and 2 teaspoons of Kaori no Kura. Ryuji explains that this alone makes a hot and sour soup because ponzu contains soy sauce and citrus acid. Heated together with the chicken stock, it becomes a hot and sour soup–style dish.

A member of the film crew asks whether heating it will make the acidity and flavor cook off. Ryuji answers that a little does, but the flavor is strong enough that it doesn't matter.

The trick is in how you handle the egg white. Egg white holds together in a clump, so loosening it a little before heating gives it the feel of the egg-drop ribbons typical of hot and sour soup. Partway through, Ryuji realizes the container is about to overflow, switches to a deeper one, and recommends that viewers use a deep container as well. No plastic wrap. It's heated for 1 minute 40 seconds at first, then warmed further for about 2 minutes 10 seconds in total. It's finished with chopped scallions and chili oil. If you want it more sour, just add more Kaori no Kura.

Microwave frozen udon for about 3 1/2 to 4 minutes. Chilling it in ice water is better if possible, but if that's a hassle, it's fine without ice. Once cooled, squeeze it firmly, since any water left in it will dull the flavor.

Add the udon to the ice-cold sauce and toss to coat. Ryuji explains that the grated garlic gives the sauce a slight thickness. Place an egg yolk on top of the gathered udon, and if you want some heat, lightly sprinkle on ichimi chili pepper. It looks nicer, and the slight kick suits summer, they say. Ryuji also jokes that if you put an egg yolk on top, the video will get views.

Ryuji says soba or Chinese noodles also work. With the acidity standing out, it's close to hiyashi chuka, but with more richness. The concept is "udon you could eat every day," and they say that in summer, something refreshing is easier to eat than something salty.

A crew member also asks whether, since this is just a base, it can be customized with vegetables and other toppings. Ryuji answers that anything that goes with hiyashi chuka, like cucumber or ham, will all go with it. At the same time, they stress that recipes with many ingredients don't get made. The most-made of their recipes, they say, is peperoncino with no other ingredients. If cucumber and ham are in the ingredient list, people who don't have them give up right there. So the fewer ingredients, the better, in Ryuji's view.

Of the hot and sour soup, Ryuji says the yuzu aroma of Kaori no Kura really comes through. It's different from ordinary hot and sour soup, tasting as if yuzu peel had been added.

Ryuji rates the udon as "insanely good." They explain that, along with the yuzu aroma, the garlic and citrus acid blend together to give it a refreshing flavor. If anyone dislikes it, they say, it would probably only be people who dislike garlic or yuzu. Their take is that a lot of people would want to eat it every day. Ponzu gives an impression of being sour, but here refreshment comes to the fore more than sourness, and it's like a punchy hiyashi chuka. Since it isn't hot, you can eat it all in one go, and it's good for when you're short on time, they say.

As for the noodles, Ryuji adds that frozen udon was used this time, but you can also boil dried noodles and chill them. The cheapest option is the pre-boiled udon sold at supermarkets for a few dozen yen, and boiling and chilling that is also an option. But Ryuji explains that they chose frozen udon this time because they figured it's what people most often have stocked at home.

At the end, Ryuji reflects that it had been a while since they cooked at the same speed as in the old days. They ask viewers who prefer this format or want to see more videos like this to respond with ratings and comments.