You can evolve a Chef using Stars earned by completing Daily Tasks from the Chef's Journal. Evolving a Chef increases their Cooking Speeds and boosts their Chef Powers.
To evolve a Chef,follow the steps below:
1. Tap on the Chef Hat icon located at the left bottom of the level map screen
2. Select the Chef you would like to evolve
3. Tap the Evolve button to evolve the Chef.

If you do not have enough Stars to evolve the Chef, you can either purchase them from the Shop or complete a few more Daily Tasks from the Chef’s Journal to earn them.