Tony Braithwaite is fast becoming the macaroni and cheese of Philadelphia-area theater. Employed in back-to-back shows all season long, and currently performing solo in Montgomery Theater's production of Becky Mode's Fully Committed, he's reliable, satisfying, and able to withstand countless variations on his basic recipe: the put-upon nice guy who may or may not come out ahead.

In Mode's frantic, comic peek behind the kitchen at a hotshot celebrity chef's Manhattan flagship, Braithwaite's Sam mans the phone bank, juggling reservations for New York's best, brightest, and pushiest. As if that weren't enough of a challenge, he's also simultaneously charged with staving off disaster in every other corner of the restaurant. If Gordon Ramsey's show depicts Hell's Kitchen, Sam's employer has banished him to hell's stockroom (designed like, well, a stockroom, by Adam Riggar). Suffice it to say that Sam, who moonlights as an actor, takes abuse from everyone, both figuratively and, yes, literally. As his agent tells him, "Sam, everyone knows you're talented. But you do tend to convey . . . a certain lack of entitlement."

Of course, every character, from Sam's agent to the sadistic top chef to Tyra Banks' personal assistant, and every other kvetching, demanding customer in between, is voiced by Braithwaite. In a challenge that's as much about acting as it is an endurance and memory test, Braithwaite keeps the show clipping along, remembering which telephone holds which call, never allowing any of his cadre of personalities to slide into one another, and somehow, perhaps most remarkably, keeping a firm hold on Sam throughout.

Among all the zaniness, Sam's recently widowed father calls to see if he'll make it home for Christmas, and it's Braithwaite's handling of these scenes that elevates Fully Committed into a play, instead of simply a show-offy impression-athon. It's a remarkable thing to watch Braithwaite swing from socialite, hostess, or sheik (47 characters in all) to a dead stop when Sam's dad's on the line. The air gets heavier, and suddenly Braithwaite is older and alone in an easy chair in some Midwestern living room, the distance separating father and son filling the room. I'm not sure whom to credit for this fine wielding of theatrical pacing - director Tom Quinn or Braithwaite himself - but I'm certainly willing to split the difference.

If there's any weakness in this quick-hit one-act, it's a too-heavy reliance on ethnic stereotyping. A customer named Wantanabe could just as easily be named Charlie Chan, and though I'm always a fan of abrasive Jewish women, there are other kinds, too. But hey, even when mac and cheese comes prepackaged, it's still pretty darn good.

Fully Committed

Playing at: Montgomery Theater, 124 Main St., Souderton. Through July 11. Tickets: $23 to $35. Information: 215-723-9984 or www.montgomerytheater.org.EndText