She enjoyed the work, and, with Priviledged as an entrée was engaged by the BBC to do some scoring for BBC films, made for television movies which, she says, are the equivalent of small theatrical films in the United States, often with strong acting and dramatic values. Among her titles were Wives and Daughters, The Falkland War, 90 Degrees South, and Cariani and the Courtesans. In 1986, she wrote the score for the British-made Jim Henson TV pilot The Storyteller, then scored eight episodes in 1987 and 1988.
She won the British Film Institute's Young Composer of the Year award in 1988, then the Carlton Award for Creative Originality for Women in Film. She was nominated by the British Academy of Film and Television Arts for her scores to The Woman in Black, the three-part drama Oranges are not the Only Fruit, and Where Angels Fear to Tread.
In 1992, the British director Beeban Kidron, with whom she had frequently worked in England, asked her to come to Hollywood to score her film Used People, starring Shirley MacLaine and Marcello Mastroianni. She has continued to work with Kidron. In the same year, Portman wrote the music for Benny and Joon and for Ethan Frome.
In 1993, she wrote the music for a large-scale Hollywood film about the stories of four Chinese immigrant families in San Francisco, The Joy Luck Club, giving her an opportunity to use mildly ethnic influences in her music. She also scored the Australian film Sirens, which starred Hugh Grant.
In 1995, she married the film director Uberto Pasolini; they have had two daughters. In 1996, she wrote the score for Emma Thompson's adaptation of the Jane Austin novel Emma, and for that project she won the Academy Award. She has since been nominated again, for the 1999 film Cider House Rules.
In an age of synthesizers, Portman continues to compose, in the main, in an old-fashioned way, at a piano keyboard with pencil and music paper. Unlike most film score composers, she also fully orchestrates her own music. Her scoring approach generally passes by the typical Hollywood string sound, although her strings can have their own approach to lushness. Lithe rhythms, a generally non-aggressive use of harmonies and rhythms, a strong ability to delineate characters with distinct themes, and a wide emotional palette characterize her work.
However, she does not conduct her scores on the soundtracks. She insists that click tracks (which she thinks make the rhythms of the music sterile) not be used. This makes the job of synchronizing the music exceptionally difficult, so she gives the task to trusted experienced conductors.
Her favorite score, and the one that was the strongest professional challenge for her, was for the film Beloved. Director Jonathan Demme insisted that no traditional European instruments be used, so she brilliantly used African and other ethnic instruments, mostly percussion, from around the world. Since that film and Cider House Rules, she has written scores for The Closer to You and The Legend of Bagger Vance.