A Paris bistro and its Michelin star: was it the cream?

Michel Petit is perplexed.

As a child, he worked to learn the restaurant trade as a waiter and cook at his grandfather's bistro in the heart of Paris near the old Les Halles market. And for 22 years now as patron, he has put in long hours perfecting Benoit's recipes and warm atmosphere, succeeding so well that he has earned the reputation from critic Christian Millau as ''the pope of bistros.''

But last year Benoit lost its star in the esteemed Michelin guide book, the bible of French cuisine, only to regain it this year.

To this day, Mr. Petit does not know why.

In the mysterious world of French cuisine as defined by Michelin, no explanations are given. Since 1900 when the huge tire company decided to put out a guide book rating restaurants with one, two, or three stars, a team of secret inspectors has roamed France deciding what is acceptable cuisine and what is not.

So Mr. Petit has only his suspicions of where he went wrong.

''We are traditional and that is probably what hurt us with Michelin,'' he speculates. ''They have a lot of young people who want what's chic. We are not chic.''

For a long year he feared that the old-style hearty cuisine in which he specializes, heavy on cream and butter, was losing ground to the light sauces of nouvelle cuisine. He also worried that Benoit's bistro formula - ''lively, warm, and informal'' - was being replaced by restaurants that opted for more formal surroundings.

Mr. Petit's regained star may signal the waning of the nouvelle fad that swept this country during the last decade. It is now being criticized for taking the taste out of French cuisine.

Even the famed chef Paul Bocuse, one of nouvelle's founders, recently decried the new cuisine's habit of using minced or pureed vegetables to thicken sauces instead of the traditional flour. ''You'd think the French had no teeth,'' he said.

But Michelin, not Bocuse, is the final arbiter. The red guide is present in almost every French automobile. A Michelin star, then - only about 600 restaurants in all qualified for at least one this year, while only 21 received three - can mean prosperity or famine for a restaurant.

Benoit's reputation as one of Paris's best bistros was secure enough to weather the Michelin shock, Mr. Petit said. Still, losing a star was a distressing experience.

Loyal customers sent him sympathy messages. ''It didn't hurt me so much in the wallet,'' Mr. Petit said, ''but it hurt me so in the heart.''

Petit does seem to love his work. Dressed in the classic bistro outfit of black vest and bow tie, white apron and shirt, the blond-bearded patron hauls his big frame around to every table to take orders.

He is like a knowledgeable companion, giving every customer a rundown on the dishes, and advising how they should be mixed.

''That fish is OK for starters, but it doesn't go down right in the middle,'' he will say, for example, emphasizing his traditionalism.

Benoit's charm lies in this frankness and informality. When Petit's grandfather opened the bistro in 1912, it was startlingly simple. ''He was a butcher by trade, so the place became known for its good meat,'' the grandson says.

Since then, Benoit's has evolved into a real restaurant. The decoration is belle epoque, with red sofa seats, wood paneling, mirrored walls, and white-lace curtains.

Still, everything is informal. Dogs lie at their masters' feet, diners are seated close to each other. They talk loudly and laugh frequently. And the waiters laugh with them.

The kitchen does not emphasize creating extraordinary works of art, but rich and savory fare. The food glows with freshness. After the main course, there is a plate of cheeses as large as a good-sized table to choose from, and a set of tarts with fresh cream poured over them. Petit fours are served with a thick espresso to finish.

Mr. Petit is largely responsible for all this. He often rises early in the morning to go to the market, then spends his days in the kitchen perfecting the recipes with the chef and evenings serving customers.

''I don't know how much I work,'' he reflects, ''but it is a lot more than the 39 hours Mitterrand is advising.''