April 20, 1983

Continuing the trend of regional acquisitions by national financial organizations, Paine Webber Inc. said yesterday that it signed a letter of intent to buy the Rotan Mosle Financial Corporation, the leading regional brokerage house in the Southwest. The transaction calls for the Houston-based Rotan to receive 1,490,000 shares of Paine Webber stock, valued at about $80 million. In recent months, national financial organizations that are seeking to grow have been looking at regional brokerages. ''In my travels around the country, a number of these regional brokerages bring up the fact that they're constantly being approached,'' said Perrin Long, a securities industry analyst with Lipper Analytical Services. ''So I would think there's good competition for them.''

THERE are certain dishes I've had just once that were so good the taste of them lingered in my mind long afterward. Among these are two Korean specialties that were first prepared for me years ago in Seoul. Their names, when transliterated, are sin-sul-lo and koochul-paan. They're rather elaborate dishes that are traditionally served for special events. Koo-chul-paan is an appetizer. The word literally means nine-hole or nine-section dish, which refers to the way it is usually served - in a lacquered octagonal container resembling a wooden candy box with a lid. When the lid is lifted, there is a center section in which small, round, thin pancakes are stacked. Around the center are eight receptacles that hold various savory, finely shredded foods to be added to each pancake before folding, dipping into a mustard-soy sauce and eating. The fillings can vary from table to table but normally include such things as shredded beef, mushrooms, carrots and cucumbers.

Lech Walesa was questioned by the police today, the third time in less than a week, amid indications of official concern over a call by underground leaders of Solidarity for demonstrations on May 1. A joint statement by the Communist Party's Politburo and the Government warned of a ''desperate adventurist attempt to incite incidents that have not happened for a long time.'' Calling for a ''responsible attitude,'' the statement said such acts could ''cast a shadow'' over preperations for the visit of Pope John Paul II in June. ''Society can count on the institutions of order,'' the statement said. Mr. Walesa has been defying the authorities by announcing last week that he met with the Solidarity underground leaders, who have called for the May Day demonstrations, and by saying that he intends to do so again.

Mayor Koch, saying he was disappointed by the low number of black and Hispanic people hired by some city agencies, prohibited his commissioners yesterday from filling most jobs that pay $20,000 or more a year until he had time to recommend applicants. In response to questions, Mr. Koch said his action was in part motivated by criticism that he has been insensitive to black and Hispanic New Yorkers. Such charges have been frequent since Mr. Koch took office in 1978, most recently over his successful backing of Deputy Mayor Robert F. Wagner Jr. as the city's next Schools Chancellor. ''It is a consideration,'' the Mayor said in describing the relationship between his order and the criticism over Mr. Wagner's selection as Chancellor. ''It is not the consideration.''

The bodies of two teen-age girls were unearthed on Staten Island yesterday, and the authorities linked their deaths and those of three other people to a man who served 16 years in prison for the murder of a municipal prosecutor in New Jersey. The suspect, Richard F. Biegenwald, 42 years old, was paroled in 1975. He was arrested three months ago in one of the killings, that of a young woman in Asbury Park, N.J., last August, and is being held in Trenton State Prison. The girls' bodies were discovered in the rural Charleston section of Staten Island. The bodies, one mutilated and both wrapped in green plastic bags, were lifted from under 30 inches of mud next to a small frame house that was occasionally occupied by Mr. Biegenwald.