AFTER WORKING for several years in a restaurant, I find it hard to imagine that a chef could be entertaining. All those hours in front of a hot broiler give most chefs the sensitivity of Attila the Hun -- and that's on a good day. But it's not that way at Benihana of Tokyo.

Benihana chefs have fun with their hungry guests. And the guests can have some have fun with them. That's partly what makes the chefs so agreeable.

"So. Where'd you learn to do that?" asks a guest trying to mask his amazement as Jason the chef blurs his knife for a few seconds at the Bethesda Benihana outlet, sending a whole onion into a zillion pieces.

"McDonald's," says the chef, coolly. "That's where I got all my training. At McDonald's."

Not only is this unbelievable, it's untrue. Most chefs at this Japanese steakhouse get several years of formal training and plenty of experience at various Benihana outlets in the U.S. or in Japan before coming to Bethesda. (Jason grew up in Seoul, and got his training in Atlanta).

"Ever miss and hit anybody with that knife?" asks another guest seated at the eight-place, griddle-topped Teppenyaki table, where diners watch intently as the chef ceremoniously cuts the strip steak, shrimp, chicken and lobster tails that each diner orders.

"Only a little ol' lady a couple of weeks ago. But she was okay," Jason says. "Customers come here at their own risk."

Then he grins to let everyone know that he's just cutting up. Jason says later that what he likes best about his job is "that I have communication with the customers" and that their response to his "act" is gratifying. His only tableside mishap, he says, was a mid-air collision of salt and pepper shakers; he assures that no one was injured.

"We have two or three [chefs] that we never know what they are going to say," laughs the restaurant's assistant administrator, Patsy Biller.

Most of the restaurant's clientele are families or groups of friends celebrating a special occasion. At Benihana, Biller says, the show is nearly as important as the food quality -- boss' orders. The boss is Rocky Aoki, 47-year-old self-made millionaire who now lives in Tenafly, N.J., and Miami (when he isn't racing speedboats or setting records for crossing the Pacific in a balloon). And a man like that generally gets what he wants.

BENIHANA -- 7315 Wisconsin Ave., Bethesda. 652-5391. Open for lunch Monday-Friday, and 5:30 to 10 Sunday-Thursday, till about 11 p.m. on Friday and Saturday. Lunches $4.95-$8.25; complete dinners $10.50-$19.50.