The top 24 contestants enter the MasterChef Australia kitchen for the very first time. First up tonight, the contestants face the classic mystery box challenge, but there's a surprise in store.

This episodes challenge is to cook Mexican street food for a huge crowd of 500 guests, with three and a half hours to prepare and ninety minutes to serve as many people as possible.

The amateur cooks are given one hour to recreate their signature dish for the first of the two judges' auditions. The judges introduce the nine past winners of the program, who are there to cheer them on.

These immunity rounds involve sauce, secrets and citrus. A contestant will face off against an established chef that will be kept secret from everyone, including the judges, until the very end.