In 1935, Fazer bought Kalastajatorppa and began to plan a new building. The new Kalastajatorppa restaurant opened to the public in July 1939 when the Colonial Hall and the symbol of the restaurant, the Round Hall, were commissioned. With terraces, Kalastajatorppa could serve 2,000 customers at a time, being the biggest restaurant in the Nordic countries.
Kalastajatorppa also played a role in Tove Jansson’s and Fazer’s common history. The first evidence of cooperation between Tove Jansson and Fazer dates back to 1937 when, according to her notes, Jansson created "a decoration for Fazer Munkkiniemi." This refers to Kalastajatorppa. According to tradition, Jansson lived in Kalastajatorppa and, because she could not always afford the rent during the early days of her career, she would pay her rent in paintings. Kalastajatorppa still has Tove Jansson's paintings on display and one room is decorated with wallpaper painted by Tove Jansson.
When the war broke out in 1939, the commander-in-chief Mannerheim suggested that Kalastajatorppa be turned into a military hospital. The building served the Defence Forces during the Continuation war as well. After the wars, the restaurant’s operations successfully continued. In 1952, Kalastajatorppa was sold to the Yhtyneet Ravintolat company.