A TikTok video from 2021 by @ohana_trender showed that Panera's soup comes in frozen packets, which came to a surprise to those who believed the soup was made in-house.
According to a Panera employee on Reddit, Panera's soups are made off-site in a factory and transported to the restaurants while frozen in pre-portioned packets.
These are then warmed in a rethermalizer, which uses hot water to heat and cook products evenly. Many other fast casual restaurants use the same method.
Panera Bread spokesperson Jessica Hesselschwerdt told USA Today that the reason for using frozen products was to keep them fresh without the need for additional preservatives.