Last night’s installment of the Harvard Science & Cooking lecture series began with Momofuku Milk Bar chef/owner Christina Tosi doling out cornflake chocolate chip marshmallow cookies to the audience. It ended with Tosi and director of culinary operations Jena Derman demonstrating a few steps of their many-layered chocolate chip cake. Somewhere in between, there was an intense creaming of butter and sugar and a discussion of Milk Bar philosophy.
The stated topic of "Emulsions and Foams" wasn’t overtly discussed much aside from a quick introduction, although Harvard’s Michael Brenner, who hosts the lecture series, closed the talk by noting that almost all components of the cake were emulsions. For a primer on emulsions — put simply, mixtures of liquids that don’t readily mix on their own — consult the recap of last year’s lecture by Nandu Jubany of Can Jubany.
What she does at Milk Bar is "home baker meets someone who went to culinary school."
Milk Bar is about to turn six years old, and Tosi has been with Momofuku for about nine years, originally hired in the operations and "odd jobs" realm before ending up baking. She was raised by women who loved to bake, Tosi told the audience last night, and she became obsessed with it herself when she was just five or six years old. Even though "pastry chef" can sound fancy and she certainly has the training, Tosi’s "spirit and heart" are in the baked goods she grew up with, and what she does at Milk Bar is "home baker meets someone who went to culinary school."
There’s plenty of technique, but the end results are fun and down-to-earth, and they bear resemblance to treats you may remember fondly from childhood. Milk Bar’s birthday cake, for example, is inspired by Funfetti cake mix. The Cereal Milk comes from a picky young Tosi’s childhood deal with her mom that she could eat all the cereal she wanted as long as she drank all the milk leftover at the end. The Cereal Milk, aside being bottled up for drinking straight, lends itself to a lot of other Milk Bar recipes because it’s a good way to "approach vanilla without giving someone vanilla." Instead of vanilla ice cream, there’s Cereal Milk ice cream. Or Cereal Milk ice cream cake. Or even Cereal Milk panna cotta.
"If you’re going to call something ice cream, it damn well better be ice cream."
Along the lines of the absence of plain vanilla, you won’t find classic baked goods or pastries at Milk Bar — no cheesecake, no chocolate chip cookies, no apple pie. When it comes to traditional items, everyone already has a favorite. Tosi asks: why would Milk Bar try to create a chocolate chip cookie when her grandmother’s are decidedly the best already? Offering something people know comes with certain expectations. "If you put something on your menu, it’s a promise," she said. "If you’re going to call something ice cream, it damn well better be ice cream."
Instead, she and the team strive to take things to another level. Instead of making cheesecake, they make a "liquid" cheesecake that becomes just one component inside of another cake recipe. Instead of selling cinnamon buns, they turn them into soft-serve ice cream. "We like to challenge what exists and why it exists," she said. "It’s the spirit of curiosity."
There are breads that resemble croissants in shape, but they’re another beast entirely. "Obviously we’re in the business of stuffing things in bread," Tosi said, describing a few of their wares. These include a bread made with a kimchi butter and stuffed with blue cheese, or the volcano, a "flavor explosion" that includes potato gratin, caramelized onions, pancetta, bacon, and gruyere.
"Paddle the heck out of the butters and sugars so that they can like each other."
After the run-down of the Milk Bar philosophy and some details on its repertoire, Tosi and Derman launched into a demonstration of the cornflake chocolate chip marshmallow cookies, a recipe that involves an astounding 10 minutes of creaming together the butter and sugar at high speed. "We are agitating that sucker," Tosi said. The recipe uses a lot more butter and sugar than most other cookie recipes, so you have to "defy all elements of the universe" to make it all fit and combine properly, Tosi explained. If the bonds don’t form during that first crucial creaming step, the cookies will fall flat. Some of the butter will cook right out, and you’ll find it on the baking sheet, not in the cookies where it belongs. Greasy cookies; wasted butter. "Paddle the heck out of the butters and sugars so that they can like each other."
A note on butter: Tosi uses Plugrá, an unsalted European-style butter. She swears by unsalted as opposed to salted because it allows her to control for the salt content in a recipe by considering only the actual added salt. And regarding European-style butter, the dairy is cultured before churning (unlike in American-style butter), adding a certain depth of flavor.
Getting back to the cookies, the egg is added after three or four minutes, and it should be cold to help counteract the friction caused by the high-speed creaming. (If the mixture gets too hot before everything is properly combined, the butter can liquefy.) Here’s an emulsion in action: the fat from the butter needs to combine with the liquid from the egg. Egg yolk is a great emulsifier due to its lecithin content, so it helps the process along. (Note that butter itself is also an emulsion — water suspended in oil, made relatively stable through the churning process and with the help of milk proteins, which are emulsifiers.)
Finally, after 10 minutes, the mixture is light, fluffy, and glossy. It’s time for the flour; the Milk Bar team uses all-purpose, but it’s a high-protein variety that approaches bread flour. This gives all that extra butter and sugar a little bit more to bond to.
At this point, it’s important not to mix much. You’re not making bread, after all, and if you mix too much, the proteins in the flour will start linking up to form gluten. Get the mixture just to where it’s a "weird, shaggy" texture that doesn’t look properly mixed. There are still a few dry ingredients to add: cornflake crunch, mini chocolate chips, and marshmallows. Once everything’s in, mix it until it’s fairly homogenous, then bake. When done properly, this recipe — and Milk Bar’s other cookie recipes as well — yields a cookie with a fudgy center and a crispy outside.
"We're comfortably human. We're perfectly imperfect."
As for the layer cake, Tosi prefaced the demonstration by speaking about the "funny" appearance of Milk Bar’s cakes, which don’t have frosting on the sides. She wasn’t quite a fan of the cake unit in culinary school ("I went to culinary school to eat," she joked) and has no use for some of the fussier, "frou frou" European-style techniques. Plus, Milk Bar cakes have so much effort put into the many layers, which include a variety of textural differences ("Why not question what can or can’t be a layer in layer cake?" she asked), so why hide them underneath frosting? "We’re comfortably human," she said. "We’re perfectly imperfect. I’m not gonna cover the sides."
The chocolate chip cake includes passionfruit and coffee components in addition to the chocolate chips; it’s "a riff on a fancy pastry chef triumvirate of flavors" done in Milk Bar’s "comfortably human way." Buttermilk is another important ingredient, partly for flavor and partly to provide acid for the baking soda to react with, creating foamy bubbles and contributing to the cake’s height. "The butter and the sugar and the eggs get really pissed" when you add the buttermilk, Tosi warned, but it has to go in, and the next ingredient — grapeseed oil — helps. "The oil is the social lubricant for the party that’s happening," she explained. The mixture will initially look a little curdled after the buttermilk is added, but the oil will fix it.
Another key to this cake (and most cakes) is a soak. In this case, the cake is soaked with passionfruit puree. A lot of non-Milk bar recipes recommend simple syrup for a soak, but Tosi sees that as a "missed opportunity to add flavoring" to a cake. "Simple syrup doesn’t taste like anything," she said. "It’s sugar water, and we’re not hummingbirds."
Running nearly an hour over the usual lecture time thanks in part to a wide variety of enthusiastic audience questions, Tosi and Derman quickly finished assembling the layers of the cake, revealing one more secret: it doesn’t matter what the bottom layer looks like. In fact, it generally looks like a pile of scraps, because that’s what it is.
The Harvard Science & Cooking lecture series continues next Monday, November 10, with Daniel Humm of Eleven Madison Park on "Where Is the Acid?" The event is free and open to the public; seats are first come, first served. More details can be found on the Harvard website.