He started to practise the vegetarian diet proposed by Maximilian Bircher-Benner, credited for coming up with the original recipe of Bircher Muesli.

[2] In 1903, the Vegetarierheim AG was in economic difficulties and Ambrosius Hiltl took over as the Managing Director and revamped the place as a vegetarian restaurant.

The restaurant began to run better, the daily turnover rose to 35 francs, and in 1904 Ambrosius Hiltl married Martha Gneupel and together they took over Vegetaria AG.

Significant changes came over in the menu when Leonard's wife Margrith Hiltl traveled to India, attended the vegetarian congress in New Delhi and studied Indian cuisine in great detail.

The then Indian prime minister Morarji Desai dined at Hiltl on his official trips to Switzerland.

The restaurant introduced an online reservation system and was positively reviewed on major internet sites.