The Milwaukee brewery’s fourth barrel-aged release aims to capture the deliciousness of Irish coffee – with an espresso variant – at an event Saturday.

Third Space Brewing is picking the month of St. Patrick’s Day to release Mystic Knot, the fourth beer in its In the Spirit series of barrel-aged beers. Saturday’s event at the brewery, 1505 W. St. Paul Ave., will also feature hordes of beer geeks, an even more limited variant, and hot and cold-brew versions of the Stone Creek Coffee blends used in the beers.

Mystic Knot is an imperial coffee cream stout aged primarily in bourbon barrels, with each of Irish coffee’s ingredients represented: coffee, cream and whiskey. It’s a concept that works exceptionally well.

“This is a concept that’s been rattling around in my head for a long, long time,” Third Space brewmaster Kevin Wright said.

The key ingredient in Mystic Knot is Stone Creek’s 3 Volcanoes coffee, a bold, fairly dark roast of a Guatemalan bean that has a spicy, roasty and chocolate/cacao character, according to Marshall Welch of Stone Creek.

The beans were roasted last Friday morning, taken directly to Third Space and steeped in the beer — essentially in giant tea bags — in a stainless steel tank over the weekend before bottling. The quick-turn approach with the coffee is meant to maximize freshness; Welch noted that coffee character in beer fades with age and also often turns unpleasant, reminiscent of old coffee grounds.

Using hyper-fresh coffee also minimizes the risk of contamination, Wright said, which can be an issue with coffee beers and is of particular concern for one that will be sold for $20 a bottle.

Third Space Brewing will release Mystic Knot, an imperial coffee cream stout aged primarily in bourbon barrels, on Saturday at the brewery. Photo by Chris Drosner

Before the coffee, though, came the “Irish” part of the Irish coffee stout: the barrel-aging.

Wright said the original plan for the Mystics was to put them into barrels that were pressure-infused with Jameson Irish Whiskey, specifically for brewers. But after two months, the barrel character wasn’t emerging to Wright’s satisfaction and — facing a hard deadline of a release the week before St. Patrick’s Day — he pulled the trigger and transferred the beer to Heaven Hill bourbon barrels.

While it would have been preferable to say the Mystics were aged in the landmark Irish whiskey barrels, having adequate whiskey character in the beer was more important, Wright said, and he was happy with the result.

So, what’s it like? Mystic Knot, which finished at 10.5 percent ABV, is the kind of beer you can smell from a few feet away when it’s first poured. It has an enormous coffee nose with tons of roast — an obvious testament to the value of the fresh coffee technique. The flavor is also coffee-forward, but the beer’s other elements come forward in better balance compared to the aroma. There’s the creamy sweetness from the lactose, some vanilla and oaky character from the barrel. Sharp palates may also pick up some of the baking-spice (think allspice) notes from the coffee.

But the most interesting thing about coffee stouts is that each component usually brings its own chocolate and roasty character. When done poorly, these can clash. In Mystic Knot, the sweeter approach to the beer essentially means the beer steps aside to let the 3 Volcanoes’ bold roastiness do the heavy lifting. It’s the central harmony in a beer that is thoroughly in sync.

I didn’t get to sample the Mystic Cortado variant, but it brings its own intriguing twist. It uses Stone Creek’s Green Bike, a moderately roasted espresso that presents as a little brighter and more acidic than 3 Volcanoes, and is blended with about 15 percent of Third Space’s Java Blanca coffee cream ale. The direct coffee dose is higher — about 2 pounds per barrel, vs. Mystic Knot’s 1.6 pounds per barrel — but there’s also a healthy dose of coffee in the Java Blanca. Cut with the somewhat lighter beer, Cortado finished at 10 percent ABV.

Bottles of the Mystics will go on sale for $20 at 11 a.m. Saturday and will sell out, probably by early afternoon. The Mystic Knot bottles are 750 milliliters, and limited to six per customer. Cortado comes in a 500-milliliter bottle, limit one. The Third Space crew warned against cellaring these beers because they so heavily rely on the coffee character that drops off rapidly with age.

Both Mystics will be on tap on Saturday as well, including two sixth-barrels of Cortado — double the amount of the variants available at previous In the Spirit releases. But the tappings that might warrant the most geeking-out are cold-brew versions of both 3 Volcanoes and Green Bike. They’ll be poured alongside their companion beers in a four-glass flight that will allow some fascinating flavor and aroma dissection. “The deconstruction part of that, I’m really excited for,” Welch said.

The Taqueria La Guacamaya truck will slinging breakfast tacos in the morning and its regular menu all day. Stone Creek will be on hand to sell its own breakfast items and the hot coffees in both Mystics starting around 8 a.m. for those in line. And there will be a line, at least at the 11 a.m. opening.

Third Space co-founder Andy Gehl was loath to make any predictions about what will still be available when. But he noted that at the last barrel-aged beer release, Nexus of the Universe in December, people who arrived about an hour before sales began were still able to score a variant.

Camaraderie among beer geeks and meeting of friends old and new is part of the scene at any big beer release like Saturday’s.

“These have been my favorite days we’ve had here,” Gehl said.

More Third Space doings

Wednesday, March 7 (Java Blanca release): This year Third Space is not giving short shrift to its sleeper hit from 2017. Wright’s team brewed just 36 barrels of Java Blanca last year – the smallest amount of any of the brewery’s beers so far – setting up some disappointment among fans when it became a hit. This year Third Space will be make 120 to 150 barrels of it, enough for plenty of kegs and new 16-ounce cans. Four-packs will be available at the brewery beginning Wednesday and in stores around the city next week.

Saturday, March 17 (St. Patrick’s Day): If you miss Mystic Knot this weekend, Third Space is opening at 9 a.m. on St. Patrick’s Day. There’ll be Mystic Knot on tap, food trucks for solid replenishment and free holiday-emblazoned Third Space pint glasses given away to the first 125 people who buy a pint. And no green beer.