Brian Stokes Mitchell has a way of filling a vacuum. At a time when the Broadway musical theater is hurting for strapping, John Raitt-type leading men, he has anchored such productions as “Ragtime,” “Kiss Me, Kate” and “Man of La Mancha.” Now, when cafe society is flush with chanteuses but lacks contemporary Billy Eckstines or Mel Tormes, he is making his cabaret debut. He’ll take his bow at Feinstein’s at the Regency starting tonight.

“I’ll do my best to fill that vacancy,” the man everyone knows as Stokes said in a recent interview. The theater world, which knows and employs Mr. Mitchell well, got a small taste of his nascent act at a January 10 memorial tribute to composer Cy Coleman, who died on November 18 (and whose trio Mr. Mitchell caught at Feinstein’s just weeks before the songwriter died.)

Prepared to deliver “Witchcraft,” he was at the last moment asked to sing another Coleman standard, “The Best Is Yet To Come.” He did so with aplomb and swagger, encouraging the audience to keep time. “Cy’s music always sounds better with snapping fingers,” he told the crowd.

“I think I will end up doing that in the show,” Mr. Mitchell said of the song. “It seemed to go over so well at the memorial. I usually do ‘Witchcraft.’ I might switch them up a bit in the show.” An additional Coleman touch will be provided by the late composer’s drummer, Buddy Williams, who will complete a quartet featuring Mike Renzi on piano, Lou Marini on woodwinds, and Bob Crenshaw on bass.

To prepare for the engagement, Mr. Mitchell has absorbed the helpful words of cabaret habitues, preparing a crooner’s crib sheet. “The best piece of advice, the most consistent thing I’ve heard from people – and I had already figured this out on my own, thank God – is that cabaret is a very intimate setting. It’s about people having access to me for the first time. I’m not hiding behind a character. It’s songs I have chosen, and I get to talk a little bit about my life. I get to take advantage of the fact that the audience is about two feet away.”

From two feet away, Brian Stokes Mitchell certainly looks the part of nightclub icon. His teeth, eyes, and head of dark curls all shine, and the face is so matinee-idol perfect as to almost verge on parody. In contrast to the tall-dark-and-handsome package and smooth baritone, his speaking voice comes as a surprise: The ingratiating words rush out, tumbling pell-mell over one another – as if he were the person interviewing Tony Award-winning Brian Stokes Mitchell.

The Broadway community is well aware of the Feinstein’s gig, though perhaps not as excited about it as Mr. Mitchell is. For the past year, producers have had to accept the idea that one of the few viable male stars a selfrespecting 21st-century showman can turn to is unavailable. The reason for this voluntary exit goes by the name of Ellington Tucker Kai Mitchell: Stokes and wife Allyson Tucker’s highly influential 1-year-old.

To indulge himself in the raising of his son, Mitchell has turned down such tempting offers as the lead in the Broadway musical “Dirty Rotten Scoundrels” (which began its previews one day before his first Feinstein’s date). “Eight shows a week is incredibly hard to do,” he explained. “I’ve been fortunate enough to do these high-powered roles. But what happens after three months is your life becomes about preparing to do the show. That can get wearying on your soul for a while.”

“That’s why I thought this would be fun – to get my live-audience kicks and not have it demand quite so much of my time. Doing concert and cabaret work frees you up a lot more. It’s something I’ve wanted to do for a while, but I’ve never had the time to do it.”

Master Mitchell’s first name might give you a clue to the flavor of the Regency set, which is titled “Love/Life.” “I’m doing more jazz, because that works better in that room,” Mr. Mitchell told me. “I get to use a different part of my voice. I call it my recording voice.”

“I’ve sung a whole lot of jazz. It’s my favorite style of music to sing. People don’t realize it, because they’re so accustomed to hearing me sing musical theater. I was raised on jazz. My father, from the time I was born, used to get up early on Saturdays and Sundays and put on Count Basie, Duke Ellington, Kenny Burrell, Sarah Vaughn, John Coltrane – all these great, classic albums. I realized as I got into my teens that I had absorbed it through osmosis, because it’s not something I studied.”

Should the Feinstein’s date go well, he hopes there will be more small stages in his future. That doesn’t mean, however, that Broadway won’t one day soon pay his son’s preschool tuition. What sort of project would appeal? This most friendly of men, who has made his name playing anarchists (“Ragtime”), pompous blowhards (“Kiss Me, Kate”), and delusional lunatics (“Man of La Mancha”), would next like to play a sociopathic murderer.

“One of the things I’ve been talking of doing for some time, if we can get all the pieces together, is ‘Sweeney Todd’ on Broadway. Christine Baranski and I did it at the Kennedy Center as part of the Sondheim celebration. So we’re trying to make the necessary arrangements.”

Until then, the void he left on Broadway – unlike the martini-sipping February faces at Feinstein’s – will continue to yawn.

Until February 19 (540 Park Avenue, at 61st Street, 212-339-4095).