This Mad Science Experiment Is the Key to the Perfect Mint Julep

Got a spare rotary evaporator lying around? Then you can celebrate the Kentucky Derby in style.

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Peter Frank Edwards

Sipping a mint julep (or six) on Derby Day is like guzzling Guinness on St. Paddy’s or eggnog on Christmas: The booze is so synonymous with the holiday that you forget why you actually drink the stuff to celebrate it in the first place. ( Churchill Downs founder Meriwether Lewis Clark, Jr. harvested his own mint outside the track’s clubhouse in the 19th century, for the record.) If Seabiscuit and seersuckers don’t excite you, then at least you have bourbon to commemorate the Kentucky Derby.

But here’s the thing about the mint julep: Set aside its storied history and you’re left with a cocktail that’s gotten a bit stale. No disrespect to the divine julep formula—it’s hard to mess up mint + bourbon + sugar + ice—but once you’ve had one kind of julep, you’ve pretty much had ‘em all, even if it comes from the mind of a master mixologist.

At least that’s what we thought.

Turns out it is possible to concoct a julep that isn’t just new and exciting, but downright innovative, too. All you need is a little bit of science, a lot of bit of creativity, and maybe a few thousand bucks.

Chartreuse: The Unlikely Star of the Show

Jayce McConnell is the bar manager at in Charleston, South Carolina, and a self-taught spirits whiz who has drawn accolades from cocktail connoisseurs in the lowcountry for his wildly inventive takes on old-school libations. So when McConnell was approached to participate in and come up with a creative riff on the mint julep, he happily obliged and fully prepared to go overboard.

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Jayce McConnell, Bar Manager at Edmund's Oast in Charleston, South Carolina.
Sully Sullivan

McConnell knew he wanted to use as the drink's base—a perfect bourbon for the julep, given its rich caramel character and lack of spice, which clashes with the sweetness of the mint—but tailor his recipe around , a strong, strange spirit with a surprising history.

Back in the 1600s, the French military passed along a recipe—one that purported to prolong life—to Carthusian monks near Paris. After the manuscript made its way to the monks’ bosses at their main monastery in the Chartreuse Mountains, they decided to produce the potion from alcohol, sugar, and 130 mystery plants and flowers.

While the monks obviously intended for their mix to be used as medicine, somewhere along the way, some genius realized Chartreuse could also get you sloshed. The rest is (shrouded) history: The Carthusians themselves have been making the stuff in secret ever since, refusing to let anyone else in on the distilling process. To this day, just two monks know the actual recipe.

Whatever the hell is in it—popular guesses include peppermint, thyme, cinnamon, and various flower tops—the enigmatic herbs fuse together to form a big, flavorful liqueur with an eye-popping, bright green color.

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Chartreuse liqueur is still made by Carthusian monks.
Chartreuse

“It’s so much fun to play with,” McConnell says. “You can work with it in a big spirit because it’s boozy and assertive, but it’s also sweet, so you can use it in the place of a syrup and it still stands out because of its crazy, herbaceous profile.”

It would be one thing for McConnell to merely use Chartreuse as a beautiful, boozy sidekick to bourbon in his julep, but he had a better idea for what to do with the liqueur.

The Experiment Begins

McConnell doesn’t know where the inspiration came from to top his tipple with alcoholic Chartreuse powder—“It just popped in my head,” he says—and, truth be told, he didn’t exactly know if it was possible, either. If you turn a liqueur into a powder, does the flavor carry through or simply morph into diluted mush?

McConnell consulted a few bartender buddies with equally mean science streaks, and none of them had ever attempted anything like it. Still, he retreated to his makeshift lab to mess around.

The first piece of gear McConnell grabbed was a rotary evaporator, a device sometimes found in chemistry classrooms. Rotovaps remove solvents from compound mixtures via evaporation; McConnell wanted to use the machine to boil the Chartreuse at a lower temperature than its normal boiling point so that he didn’t have to cook it.

“The reason you want to do this is because if you cook Chartreuse, you caramelize its sugars, which creates a burnt sugar flavor and turns [the resulting mixture] brown,” McConnell says. This is what you’d most likely find if you tried the experiment on a stovetop.

He fetched his machine from a Japanese website for around $1,500, but you can , as well as accompanying equipment, on Amazon.

To start, McConnell pumped the Chartreuse into the glass evaporation flask seen in the photo below. Then, he heated the liquid to 65 degrees celsius (149 degrees Fahrenheit), a temperature he arrived at simply through trial and error. (“If you set it too hot, the Chartreuse might boil over,” McConnell says. “Too cool and it’ll take too long.”) The water bath underneath the flask provided the heat.

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McConnell’s rotary evaporator.
Jayce McConnell

Next, he set the flask to rotate at a rate of 17 revolutions per minute (rpm)—more trial and error—which increased the surface area and made it easier on the liquid inside. Why’s that important? “Because the whole point of this is to gently cook the liquid to promote smooth evaporation,” says McConnell. “If you don’t rotate the flask, you can overheat the liquid.”

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The water-driven pump sucks air out of the rotovap and cycles cold water through the condenser coil.
Jayce McConnell

The next step was turning on the rotovap’s water-driven vacuum pump, as seen in the photo above. This part pumps air out of the rotovap, creating a vacuum and sending cold water into the condensing coil, as seen in the photo below. This is all to re-condense the evaporated Chartreuse, just like in a still, McConnell says.

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The condenser coil.
Jayce McConnell

As the chartreuse warmed up and the gravity inside the rotovap lowered due to the vacuum, the alcohol in the rotovap began to evaporate. It then traveled up to the condensing coil, where it turned back into liquid and into the receiving flask. Then it was time for the rotovap to work its magic.

The Power of Powder

After about a 48-hour waiting period, McConnell was left with a nearly alcohol-free base in the rotating flask and an almost-even amount of clear alcohol in the receiving flask, since Chartreuse is 55% alcohol by volume (ABV). Now it was time for him to make the powdered sugar.

McConnell took the mix from the lab to the kitchen, combining a “big batch of egg whites” and two cups of sugar to make a thick paste. Once he added the Chartreuse to the paste, he thinned it out with a spatula, spread it onto a sheet tray, and threw it in his dehydrator at approximately 180 degrees Fahrenheit.

Over the next day, McConnell periodically checked in on his creation, stopping to break it up as needed. After 24 hours, all that was left to do was turn the dehydrated chunks into powder. One quick buzz in the blender later, and McConnell’s masterpiece was complete.

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The final powder product.
Jayce McConnell

We know what you’re thinking: That’s a comical amount of blood, sweat, and sugar just to cook up some powder, right? Even McConnell admits the experiment was excessive. “Ninety percent of this was just to look cool and have a little story,” he says.

But ah, that other 10 percent. When you sprinkle some green, boozy powdered sugar on top of your mint julep as a garnish, “it tastes really cool, too,” McConnell says. “It adds a sort of mysterious, herbaceous flavor to the drink. And you can lick it off the mint leaves.”

McConnell’s got plenty of the stash stacked behind the bar at Edmund’s Oast, so if you want to try his original cocktail, hop on a flight to Charleston. If not, simply sub out McConnell’s sugar for regular confectioners’ sugar in the recipe below; thanks to the exotic Chartreuse and wheaty Maker’s Mark, it’ll still be better than any mint julep you’ve ever had.

But if you’re bold enough to step into your own booze lab and emulate his experiment, “I don’t see why you can’t have a little fun and stir things up,” McConnell says.


The Recipe: Carthusian Julep

Created by Jayce McConnell for Edmund's Oast

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The Carthusian Julep.
Maker's Mark

  • 1 oz. Maker’s Mark® Cask Strength Bourbon
  • 6 mint leaves
  • ½ oz. green Chartreuse®
  • Pebble ice
  • Mint sprigs
  • Thyme
  • Chartreuse powder

    To prepare the mint julep mixture, muddle the mint leaves gently with Chartreuse in the bottom of a cup. Then, add the bourbon and fill halfway with pebble ice.

    Stir these ingredients briefly and then add a metal straw and pack the glass full of pebble ice. To finish, garnish with lots of mint and thyme; dust with Chartreuse powder.

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