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You're listening to SHORT WAVE from NPR. Today on SHORT WAVE, we have cooked up something special for you. Literally.

Is it cool the peppercorns are splitting? Like, they're exploding from the heat.

Making delicious food and sharing it with people is something that I love. And you know who's phenomenal at this? Kenji Lopez-Alt.

KENJI LOPEZ-ALT: Like, I literally cooked two different dishes this morning. One of them was pad kra pao - so, like, Thai pork with basil - and the other one was mapo tofu - Japanese-style mapo tofu.

KWONG: Kenji has a metaphor to describe his cooking philosophy. He compares tackling a new dish to navigating a new city.

LOPEZ-ALT: And you can just stand there and walk down the street staring at your phone and turn when it tells you to turn. But you won't really have an understanding of what the city is like, of how you got there, what the neighborhood is.

KWONG: That's what following a recipe is to him. Yeah, it will take you from Point A - raw ingredients - to Point B - the final dish.

LOPEZ-ALT: And, you know, that's fine for some people. But once you start to understand sort of technique and science, that's more like being given a map. I can take whatever route I feel like taking or I can wander around.

KWONG: And as a cookbook author, Kenji has thought a lot about this - how to teach people science-guided techniques to cook in new ways.

LOPEZ-ALT: It allows you to sort of plan your own route and take charge of your own cooking.

KWONG: And now he has written a book all about his favorite pan in the kitchen, the wok.

LOPEZ-ALT: The wok that I have in my kitchen, I bought it when I was in college - so 20-something years ago.

KWONG: And for the last 20 years, Kenji's wok has had permanent residency on his stovetop. He cooks with it multiple times a week.

LOPEZ-ALT: I've been with my wok longer than I've been - longer than I've known my wife.

KWONG: In his book, aptly titled "The Wok," Kenji Lopez-Alt explores recipes and techniques in detail, sprinkling science into his cooking directions. So today on the show, we're going to light those burners and pull out the fancy oil for the coolest pan in the kitchen, according to science.

LOPEZ-ALT: It's the most versatile pan in the kitchen.

KWONG: I'm Emily Kwong. You're listening to SHORT WAVE, the daily science podcast from NPR.

KWONG: OK, Kenji. Producer Berly McCoy and I did some cooking on our own to prepare for this interview, and we wanted to start with some wok basics. Do you know why the shape of the wok enables it to be the most versatile pan in the kitchen from, like, a scientific standpoint?

LOPEZ-ALT: Yeah. Well, so the shape of a wok is really designed to encourage evaporation. So it has, like, a very wide surface area. It has a lot of cooking surface because it's so conducive to evaporation because you have so much surface area and because the shape of it allows you to toss. And so at least when you're stir-frying, you're looking for very dry heat. So tossing and the evaporation that comes with that shape and the action of tossing is what allows you to do that and what allows you to get that sort of specific concentrated flavor.

KWONG: One of the techniques that you tell people about in the book is just simply pushing things up the sides of the wok...

KWONG: ...Because those sides are cooler. And I hadn't really thought about that, how the wok has different zones of heat...

KWONG: ...Which allows for food to stay at different temperatures, which is really not the same with a linear pan.

LOPEZ-ALT: So if you put food in a flat pan and you shake it, it ends up being in a sort of thin, even layer, right? And that's good when you're, like, searing a bunch of meat and you want all the steaks to sear evenly. You want there to be even heat across the whole surface. Whereas with a wok, you have this very intense heat at the very bottom, and then it slowly - it gets steadily cooler as it goes up the sides.

So for example, in the book, there's a recipe for pad thai - right? - where you start by cooking aromatics and then cooking the noodles in sauce. And then once the noodles are hydrated, you push them up the side and clear out the space in the bottom. And so that - the noodles don't continue to overcook, but the bottom gets really hot so that you can then fry an egg. You can push that egg up the side, you can sear shrimp. So you can do all these things in this one hot zone in the bottom of the wok without overcooking the ones that you've already cooked.

KWONG: You know, you make some really specific recommendations for home cooks buying woks - and just want to spend a minute on your suggestion of a carbon steel wok, which you say has the highest volumetric heat capacity. What does that mean? Why is carbon steel optimal?

LOPEZ-ALT: (Laughter) Well, heat capacity is essentially the amount of heat energy a specific material holds per unit temperature, right? So if you think about your pan as a bucket that's storing energy, right? So when you turn on a burner, you're essentially turning on a tap that's filling that bucket at a certain rate, right? And these buckets, they all leak, right? Your heat is going to be escaping into the kitchen. Once you put food in it, you're very rapidly pouring some of that energy out straight into the food, right? And so you want your pan to be able to hold a certain amount of heat before - so that you're not relying just on the heat input of the stove.

You want there to be this balance between the amount of energy that the pan can store so that you get some nice searing at the beginning and some nice really high heat at the beginning. But you also want to be able to adjust the heat rapidly up and down because there are many recipes where you start really hot and then you bring the temperature down and then you bring it back up at the end to reduce the sauce, et cetera. So you want - so - you know, so you want the pan to also be reactive. So carbon steel is good because it stores a good amount of energy, but it can be actually manufactured thin enough that it's still going to be reactive as well.

KWONG: And you say it's rare in Western cooking that you find yourself, in a recipe, going from a simmer to a sear to a gentle bubble in a few minutes. But in a lot of non-Western cooking and Asian cooking, that happens all the time.

KWONG: Yeah. Lastly, we're in Camp Nonstick Wok Only, yes?

KWONG: Oh. Oh, no. Sorry, sorry, sorry. What am I saying? What's the opposite of a nonstick wok?

LOPEZ-ALT: A non-nonstick wok? A stick wok? I don't know (laughter).

KWONG: A sticky wok? We're in Camp...

KWONG: Yeah, that's what it is. Yeah. You say in the book, do not buy a nonstick wok.

KWONG: You want that wok to be sticky. Why?

LOPEZ-ALT: Well, it's mainly because for many recipes, you're going to be heating the wok up very hot at the beginning in particular. So you might be heating the surface of the wok up to five or six hundred degrees, and nonstick coatings don't withstand temperatures that high. They tend to break down. And so some of them will actually start smoking and they'll turn into these horrible carcinogenic things that get into the air, you know, at temperatures above 450 degrees or so. And so nonstick coatings generally are not tough enough to withstand that kind of thing.

KWONG: Yeah. Kenji, I recently had the DC contingent of Team SHORT WAVE over for dinner. And we cooked two dishes from your book.

KWONG: And, you know, I used a wok that I own that's already seasoned. When you purchase a wok, before you use it, you talk in the book about seasoning it. Basically, you heat the wok over a flame until it turns almost a bluish-black color, and then you dry it and coat it with oil.

KWONG: Why should you not skip this step? Why should you take the time to season your wok before you use it?

LOPEZ-ALT: Well, so there's a couple things. So first of all, like, when you buy a carbon steel wok, typically it comes coated with a layer of machine oil - like, nonedible oil. So you definitely want to get that out. The other reason is that - so when you heat your wok up, when you heat the carbon - bare carbon steel in the presence of oxygen, it forms black oxide, which is that black coating that you're getting. And that imparts certain nonstick qualities to it. So that's what's going to make it so that you can stir-fry in it without things caking onto it. So, you know, nothing horrible is going to happen if you don't do that. It's just going to be - your wok is just not going to have that layer of protection that makes it nonstick. And also, it also protects the metal, so that it won't rust as easily, et cetera. And then finally, you know, if you're really going for certain dishes, there's that wok hei flavor, the breath of the wok, that kind of smoky flavor. So that's part of it, as well.

KWONG: Thank you. You're helping us be better wok owners and users. So, Kenji...

KWONG: ...We made your favorite dish, mapo tofu. What does the mapo tofu mean to you?

LOPEZ-ALT: So - OK, so I grew up eating the Japanese version of mapo tofu. So mapo tofu is a Sichuan dish, from the Sichuan province in China. But it came to Japan in the '70s, and my mom learned how to make it. And then, you know, when I was growing up in New York, my mom would make mapo tofu. And what she would do is she would make dumpling filling, right? And so me and my sisters would then make dumplings using this filling - a beef-based filling. And then whatever leftover filling there was, that would become the beef part of the mapo tofu. So she would - it always had, like, garlic and ginger and scallions and stuff in it. And so she would stir-fry that and then season it with soy - the Japanese version is soy sauce and sometimes miso paste, mirin and then soft tofu. It's - yeah, it's always been one of my favorite things. And it's a - it was a comfort food growing up. And, you know, I make it for my kids now.

KWONG: That is so lovely. Kenji, we want to play you a little audio of Berly and I making your mapo tofu and tasting the final dish.

This is the tofu in mapo tofu right here. And it's just going to gently simmer in these sauces. This did not turn out right. The other dish did. This did not. It's wrong.

LOPEZ-ALT: What was wrong with it?

KWONG: So I'll tell you what happened.

KWONG: Here's what happened. OK? I had doubanjiang, like, sauce but not paste.

KWONG: So there were these other flavors in the doubanjiang...

KWONG: And I was like, oh, no. This is not the same. And then I was like, OK, remember what J. Kenji Lopez-Alt would say. Cooking is a map, not Google. So just roll with it. And so the flavors didn't taste quite right. And so I tried to balance them by adding some more salt...

KWONG: ...To kind of just mellow out the funky flavors in the sauce.

KWONG: And over time, it kind of figured itself out and tasted right.

LOPEZ-ALT: Well, good. I'm glad it worked out over time.

KWONG: And my guests clearly didn't mind. They liked it.

KWONG: Yeah, ground beef. This is mapo tofu.

What excites you about what's happening at the intersection of science and cooking right now?

LOPEZ-ALT: I don't know. I've got two little kids, and so I don't pay much attention to much outside my house.

LOPEZ-ALT: What excites me is that - I mean, the intersection of science and cooking is that my daughter loves experimenting in the kitchen, and we talk about science while we're cooking. So that's the most exciting thing for me right now. I don't know about the rest of the world.

KWONG: That's beautiful, Kenji. Thank you so much for bringing all this information - putting it all together into one unbelievably cool book. It was so much fun to work through it and to learn from it and to talk to you today.

LOPEZ-ALT: Yeah, it was good to talk to you, too.

KWONG: And just a quick reminder. Give us feedback on SHORT WAVE by filling out our podcast survey. Now is really your chance. Go to npr.org/podcastsurvey.

This episode was produced by Berly McCoy. It was edited by Rebecca Ramirez and Gabriel Spitzer and fact-checked by Rachel Carlson and Margaret Cirino. The field engineer was Natasha Branch, and the audio engineer was Josh Newell. Gisele Grayson is our senior supervising editor, Beth Donovan is our senior director and Anya Grundmann is our senior vice president of programming. I'm Emily Kwong. Thank you so much for listening to SHORT WAVE, the daily science podcast from NPR.

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