Vocalist. She has performed in musicals at the Roma Musical Theatre: Miss Saigon (Kim), Grease (Frenchy), Peter Pan (Adult Wendy). As a guest artist, she also played Maria in West Side Story at the Musical Theatre Capitol in Wrocław and Prisoner June in the musical Chicago at the Komedia Theatre in Warsaw. Since 2017, she has been performing at the Musical Theatre in Łódź as Fantine in Les Misérables. She lent her voice to many characters in animated films and series, including The Little Mermaid, Peter Pan: Return to Neverland, Coconut: The Little Dragon, The Jungle Bunch, Maya the Bee, My Little Pony and Beauty and the Beast. She sang the Polish version of the song Let It Go as Elsa in the award-winning Oscar and Golden Globe film Frozen. Kasia is also an author and composer of songs for children. She co-created, among others, the title song for the animated series Buni, songs for the Wygibasy z naszej klasy project as well as Śpiewanki.tv and Lili i Plaf. She sang radio jingles for RMF FM, Radio Zet and Radio WAWA. In 2008–2012 she collaborated with Jon Lord from Deep Purple on the Concerto for Group and Orchestra project. In 2011, the album Jon Lord Live, a recording of a concert in Bucharest, was released on CD and DVD. Kasia Łaska performed the vocal part in the studio version of the album (released in 2012), where she sang alongside artists such as Steve Balsamo, Joe Bonamassa, Darin Vasilev, Bruce Dickinson, Steve Morse and Guy Pratt. The recordings took place at the famous Abbey Road Studios in London. In 2013, the song For My Love by her own project Sirli debuted on Radio Three as a proposal for the Hits List. In June 2018, Kasia created an original project, myBROADWAY, the live recordings of Broadway musical hits, which can be seen and heard on YouTube.