The phrase "dish of one's choice" means that someone can choose and have any food they want to eat from a menu or selection of food options. Full definition
When I first got into cooking potatoes were my side dish of choice for every family function. (staysnatched.com)
Spoon pecan crumble into the bottom of four serving dishes of your choice. (vegnews.com)
The day starts with a huge buffet breakfast with the chef standing at the end of the dining room at the «egg station» ready to cook any egg dish of your choice. (uptheclarets.com)