Down in Panda & Sons’ lab, housed in the basement of nearby sibling bar Nauticus, owner Iain McPherson tinkers with his array of freezing equipment. The Edinburgh-based bartender pulls trays of fruit from his high-tech industrial freeze dryer. “Try this,” he says, offering a taste of dehydrated apple while eyeing his Tefcold chest freezer. In this super freezer, which can reach extreme temperatures (as low as –50°C), McPherson keeps stainless steel growlers and ice coolers, each filled with ingredients to which he has applied his innovative subzero methods like “switching” and “sous pression.” Poking around McPherson’s lab—illuminated by a neon blue sign that reads “Brain Melting Society”—is like taking a tour of Mr. Freeze’s bunker.

With a couple of academic degrees in the science of ice cream, McPherson has dedicated the past few years to developing mind-bending freezing methods and applying them to cocktails. The culmination of his efforts is Panda & Sons’ award-winning cocktail menu entitled Transcend, which is divided into four sections by technique: “Switching,” “Sous Pression,” “Freeze Drying” and “Cryo Concentration.” For those who want to dip their toes into the ice-cold waters of McPherson’s processes, the last technique is most replicable.

“Cryo concentration, also known as ‘freeze concentration,’ is the OG subzero flavor technique,” explains McPherson. The method involves freezing a liquid—such as blended fruit—and removing the water content, resulting in “a more concentrated and flavorful liquid.” McPherson also likes to refer to the technique as “freeze ripening” because it’s akin to organic ripening: Water content decreases, sugar and acids increase. This is the method that Panda & Sons uses to make the Red Panda, one of its cult-favorite cocktails, served at the bar since it opened in 2013. The savory drink, which is now on its second iteration, is a twist on the Red Snapper (a gin-based Bloody Mary) made with Thai flavors that are inspired by McPherson’s time living in Thailand.

“The 2.0 still has the same ingredients as the original because we wanted to stay true to the classic with its fragrant, refreshing, spicy, umami and zingy flavor,” says McPherson. “But this time, we wanted to show how, with cryo concentration, we can pull out different flavor profiles from ingredients.”

To prep the tomato element, McPherson pours store-bought tomato juice into a 4-liter insulated cooler. Once filled, the cooler is stored in an upright freezer set to –10°C (14°F) for 24 to 30 hours so that the juice partially freezes; a layer of frozen watery tomato juice rests on top of the unfrozen concentrated juice. McPherson removes the frozen layer, leaving behind an amplified tomato component that is more flavorful and lush in texture, and can stay colder for longer because of the decreased water content.

In keeping with the typical Red Snapper structure, the tomato juice is paired with Tanqueray No. Ten gin that’s been infused with fresh cucumber and torn makrut lime leaves to add an aromatic freshness to the cocktail. A proprietary spice mix as well as salt, pepper, Worcestershire sauce and lemon juice are also added before the drink is thrown to aerate and dilute it. The final upgrade to the bar’s original Red Panda comes in the form of Guinness foam.

While the 1.0 version of the drink was served with a float of Guinness on top, McPherson says that the 2.0’s Guinness foam “adds a lovely soft bitterness to the drink, which slowly evolves as you sip.” To make the foam, McPherson combines Guinness with xanthan gum, a food foaming agent, and some black food coloring for a more distinct visual appeal. The mixture is then chilled and dispensed via an iSi whipper after being charged with an N2O (nitrous oxide) cartridge. 

McPherson feels the tweaks made to the second generation of the drink have a big impact. The new version “tastes like the 1.0, but all souped up,” he says. The indulgent Red Panda 2.0 balances vibrant citrusy aromatics, umami from the tomato, a hit of savory-sour heat from the spice mix and a delicate bitterness and textural nuance from the foam. 

McPherson will continue to delve into the relatively unexplored depths of subzero techniques; he feels his recent innovations are only the tip of the iceberg. “Over the next few years, new techniques may be realized, which will enable us to improve our cocktails, such as the Red Panda 2.0, even more,” he says. But for now, “Red Panda 2.0 isn’t going anywhere soon.”