The hottest new cocktail bar in town is hiding underneath a new restaurant in River North. Kitty’s Cosmopolitan Club, a swanky spot with modern cocktails, tableside mixing, and some of the prettiest glassware in town, has been bringing in the crowds since it opened in late March underneath Crying Tiger.

Vigilant River North watchers may remember this space from its previous iteration as Sub51, the bar/club beneath Hub51, which has since been replaced by Crying Tiger and Gus’ Sip and Dip. The cocktail program is managed by superstar mixer Kevin Beary, who also handles the drinks at Three Dots & a Dash, Gus’, the Bamboo Room, and many other Lettuce Entertain You spots.

“We knew from the start we wanted to do a high-end European style lounge,” explains Beary. “The intention was for it to feel like it was a lounge in a five-star hotel. Before Lettuce, I worked in luxury hotels, in bars and lounges. I like that style of service, the way drinks are presented.” The room certainly feels luxe, with elegant textures and pretty design touches. The glassware alone is enough to blow you away (no pun intended); it’s hand-blown and imported from Japan and Spain, and some of it was custom designed just for Kitty’s. The bartenders are also top-notch, pulling the Lettuce A-team from around the city. “Every bartender here has worked for me for at least three years,” Beary says. “These are all my leads from all the bars I oversee.”

The cocktail menu is split into a few main sections. First is the freezer portion; these drinks are pre-batched and served in glassware kept in a custom-built, super-powerful walk-in freezer. The drinks are takes on classics, but have modern touches. The Dirty Martini and a Half is served with the shaker nestled in a bed of crushed ice and a side of blue cheese deviled olives, while the vesper is topped with drops of lemon distillate that lend a bright, fresh variation to the traditional lemon twist. Other cocktails are “from the bar” (that is, mixed to order). Some drinks might sound familiar — take the Whiskey Coke, which everyone knows but couldn’t be further from the dive bar standard. Here, it’s a milk punch that’s made with Japanese and American whiskies, lemon, and sarsaparilla, then strained through whole coffee beans, carbonated, and served as a highball. It hits the notes of a whiskey Coke, but is far more nuanced. Oh, and it’s also served with a “lime,” which is actually a Jell-O shot that is a different variation on a whiskey Coke.

The tableside service component is a huge highlight of Kitty’s. Right now, there are two options; a martini made with a very dramatic pour of liquid nitrogen and a high-end old fashioned made with Yamazaki 12-year-old whiskey. If you’re an old fashioned lover, go now — Beary says that that particular whiskey is hard to get, and when the supply is exhausted, the featured drink will probably change.

While Kitty’s does offer some bites, notably a selection of dim sum and a seafood tower, it’s definitely more of a before-or-after dinner spot. But don’t plan to walk in; reservations open 30 days out, and it’s been filling up fast.