Beer cocktails are having a bit of a moment. Their rising popularity has been noted recently in sources like The Huffington Post and BBC News. But today’s bartenders are no longer content to follow the simple “beer plus hard liquor” formula of the Boilermaker or the Irish Car Bomb.

Take, for example, the Rogue Sour mixed by Dylan Fox, head barman at Barley, Wheat and Rye Social House in Springfield. Fox’s riff on a traditional New York Sour combines the pungent tartness of a Belgian lambic and the earthiness of barrel-strength rye whiskey for an aromatic, complex cocktail.

The Rogue Sour began with a request from patron Ryan Mulcahy, known locally as The Rogue Barber. When he sampled the Belgian lambic on tap, Mulcahy asked Fox if he had ever considered using it in a cocktail. After several attempts, Fox struck on the perfect combination of ingredients to fill Mulcahy’s request. A new signature cocktail was born, named in honor of the man who provided the inspiration.

417 Magazine recently named the Rogue Sour the best beer cocktail in the Springfield area. We sat down with Fox to learn how it all comes together.

Step one: The egg

Fox starts the drink with the white of an egg. The egg is locally sourced and farm-fresh, in keeping with the farm-to-table ethic of Barley, Wheat and Rye’s parent restaurant, Metropolitan Farmer.

Egg white is the key difference between a New York sour and a whiskey sour. When shaken in a mixed drink, it forms a frothy, smooth foam.

Step two: The liquids

Fox adds a full measure of Dark Horse Barrel-Strength Rye Whiskey. Produced in Lenexa, Kansas, Dark Horse is as close to local as rye whiskey gets, at least for now. At 113.7 proof, it is nearly 50 percent more potent than a typical rail whiskey.

Fox also adds vanilla simple syrup and lemon juice.  The simple syrup is infused in-house using whole vanilla beans. The lemon juice is freshly squeezed.

Step three: The first shake

Fox first shakes the mixture without ice.

“The trick to a great egg-based drink is to shake without ice,” Fox told us, “to emulsify all of those ingredients together before you introduce the water.”

Step four: The second shake

Fox adds ice and shakes again. This second shake quickly chills the mixture and dilutes it very slightly. It also produces a subtle texture by introducing the tiny fragments of ice that differentiate shaken cocktails from stirred cocktails.

Step five: Strain and pour

Fox strains the shaken mixture into a coupe glass.

Step six: The beer

Fox tops the glass with gueuze lambic. He uses St. Louis Premium Gueuze. Unlike the beer cocktails of the past, the Rogue Sour uses only 1 1/2 to 2 ounces of beer.

Sour beers are a growing trend in the craft beer market. But, for the uninitiated, gueuze is a traditional Belgian sour beer. Fermentation by wild yeast gives it a musty, sour flavor. Besides being a distinctive cocktail mixer, it is certainly worth enjoying on its own merits.

Step seven: The finish

Fox finishes the cocktail with a genuine maraschino cherry on a bamboo spear.