Portillo's Cake Shake is made with an entire slice of cake

• Portillo's is a fast-casual restaurant chain considered a one-stop shop for iconic Chicago foods.
• Founded in 1963 in the Southwest suburbs of Chicago, Portillo's is known across the country for its hot dogs, Italian beef sandwiches, cheese fries, and chopped salads.
• But its best kept secret is the restaurant's cake shake. Insider's Medha Imam visited Portillo's Summit, IL location to learn what goes into making the iconic cake shake.
• Rumor has it they put an entire slice of chocolate cake into their milkshake, making it a must-try dessert.

Following is a transcript of the video.

Medha Imam: Portillo's is known across the country for its savory hot dogs and crispy french fries. But most Chicagoans know that Portillo's best-kept secret is its cake shake.

Customer: It's a shake and it's Portillo's chocolate cake at once. It's amazing. It's an evil idea. I don't know who came up with it.

Customer: Thumbs up. Love it.

Medha: The Portillo's location here, in Summit, Illinois, is known as the chain's sweetest suburb.

Kara Crones: In this location, depending on the day, we're gonna go through anywhere from 60 to 200 of these a day probably. On the weekends, we sometimes make over 100 cakes on a Saturday morning.

Medha: That's Kara Crones. She's been with Portillo's for nine years and has been making the cakes and cake shakes ever since she started working here.

Customer: It's extremely chocolaty and decadent. It's very moist.

Customer: It's delicious.

Kara: People are still shocked when you tell them, "Hey, we bake these on-site fresh."

Medha: The cake mix starts with its dry ingredients, baking cocoa flour, baking powder, and baking soda. There's always been this rumor that Portillo's cake has mayo in it to make it so moist. [Kara laughs]

Customer: I ain't no culinary expert, but I heard mayo is a big thing on that.

Medha: Can you dispel those rumors? If it isn't true?

Kara: I can't tell you what the secret ingredient is.

Medha: OK.

Kara: Someone might kill me. No, I'm just kidding.

Medha: The real secret is in the mixing. Portillo's mixes the batter at three different rates, low, medium, and then high. This is to incorporate deep pockets of air into the mixture to give it that famous fluffy texture.

Kara: When it gets towards the end, you kinda get the start of that smell of chocolate cake. You're like, oh, it's almost done. It's Portillo's chocolate cake time. You gotta check on it towards the end, about 28 to 29 minutes, because nobody wants overcooked chocolate cake.

So, when the cakes come out of the oven, we've got to pop them out of the pan so they can finish their cooling, so they don't overcook in there. So, we're gonna just give it a good hearty tap on the side, and then we're gonna flip it into our hand, and then we're gonna take it, and we're gonna put it on this cooling rack here. And then we can frost it, because we don't want melty frosting.

Medha: The frosting that goes on a Portillo's chocolate cake is not homemade and is in fact just your traditional classic fudge frosting.

Kara: So, we're gonna first put a tiny little dot on the bottom to help the cake stick. And then we're gonna flip it upside down so that the finished product has a more even look and so the two pieces stick together. So we're almost making a hamburger out of the cake. And then what we're gonna do is we're gonna take our first pound of frosting, and we're gonna spread it out as evenly as we can.

Medha: And did you say pound of frosting?

Kara: I did.

Medha: OK, so there's 2 pounds of frosting.

Kara: 2 pounds of frosting on every Portillo's chocolate cake.

Medha: Wow.

Kara: And then we're gonna take our second pound of frosting, and we're gonna put it on top and wrap it around all the sides, but we're not really going for perfection, we're going for homemade.

Customer: I'm not into sweets, but this is good.

Customer: This is very good. All along that I've been going to Portillo's, I usually get a piece of chocolate cake.

Customer: So, you have to eat beef.

Customer: Yeah.

Customer: And beer and cake. [laughing] In that order, though. It's good. I like it.

Customer: Their frosting really does it. Some cakes, it's just kinda, like, too whippy or something.

Customer: Yeah, I'm not a big fan of, like, the whipped cream, so the frosting kinda does it. And just the cake itself...

Customer: It's super moist.

Customer: It's moist and spongy.

Employee: 281, your lunch is done.

Medha: Thank you! It hits the spot, every time. I remember as a kid at all of our family parties, we would have Portillo's cake. The cake itself isn't as overwhelmingly sweet as you would think it would be, based on what we saw in the kitchen. It's like, again, a subtle taste of chocolate, and the frosting is really what adds the sweetness to it. There's enough frosting to last you the entire cake. This is literally the perfect guilty pleasure for anyone wanting to eat their feelings. This is it.

But you can't just eat Portillo's chocolate cake. You gotta try their cake shake. According to Kara, back when Portillo's started making Gina Portillo's cake recipe, they could only serve them the day they were made, because that's about how long they stayed fresh for. So a manager by the name of Dale Phillips thought it would be a great idea to utilize the leftovers.

Kara: They started putting pieces of cake into a cake shake, and they started selling it, and it's been a success ever since. We're gonna grab our cup. We're gonna give it a tiny little bit of shake mix in the bottom.

Medha: And what is that shake mix?

Kara: Vanilla ice cream, pretty much. We're gonna take our whole piece of cake.

Medha: The entire piece?

Kara: An entire piece of cake.

Medha: [laughing] That's amazing.

Kara: We're gonna put it all in this cup with this little bit of vanilla ice cream.

Medha: OK.

Kara: The moment people find out that we put a piece of cake in a shake, their mind is blown.

Medha: My mind was blown today. I'm from Chicago, and I feel like a lot of people don't even know that Portillo's has a cake shake.

Kara: No, they don't.

Medha: And I only equate the cake shake to Portillo's.

Kara: So, the whole thing is gonna go in. We're gonna make sure they get all their delicious frosting.

Medha: This is why I love Chicago.

Kara: Then we're gonna even add some of our chocolate syrup in there. So it's chocolate on chocolate. We're gonna add a little more shake mix.

Medha: All right.

Kara: Little bit on the bottom, so the cake doesn't get stuck in the bottom and then you just get big chunks, and then a little bit more, and then we're gonna mix. It's gonna break up some of the chunks of that piece of cake that's in there so you can actually drink it through a straw or with your spoon on the side.

You wanna be able to have somebody drink this in their car when they're leaving the drive-through. You want a little bit of thick chunks in there, just for a bite, but not a lot. And then we're gonna put a little more on to top it off.

Medha: OK.

Kara: And then we're gonna mix. And voilà, chocolate cake shake.

Customer: It's chewy. It's good.

Customer: It's good. [laughs]

Customer: Now I don't know. [laughing]

Customer: I like it when you get the chunks in there, and especially if it's, like, the chunks of frosting, oh.

Customer: Yeah, chunks just... [sucks] [laughs] Gotta suck extra hard.

Medha: The rumors are true. They do indeed put an entire cake slice into the cake shake, which is amazing. And the best part of the cake shake, for me, at least, is that each sip comes with bits and chunks of the chocolate cake itself, so it really feels like you're drinking an entire cake slice. I know that sounds like a lot to some people, but it's so yummy. It's so tasty. And I recommend it 100%.

The best thing that complements the cake shake at Portillo's are the fries. You literally dip the fries in your cake shake, and you take a bite. And you get the perfect combination of sweet and savory, you get the crunch of the fry, and the soft mushiness of the cake shake itself. So good.

Portillo's for me as a kid was always comfort food. It was always something that reminded me of home and a place where I could come with all my friends. Whether I was in high school, whether I was in college, there was just so much variety, but also the food was just always good. Especially the cake, the cake shake, and the fries. These three might not be on the iconic five list of Portillo's, but to me, they're the famous three.

This is why I miss Midwest. No one cares about the calorie count. You just taste good food, and you eat good food, and you just eat what makes you happy.