Fermentation research has traditionally concentrated on free-floating microorganisms. In contrast, biofilms are commonly seen as a contamination danger. However, many food fermentations, like kombucha, cheese rinds and koji, rely on surface-attached populations. This review defines sessile fermentation as the purposeful utilization of controlled biofilms as functional aids in food systems. We combine biofilm biology and process engineering to describe how natural biofilm fermentations maintain stability and safety. Key processes include diffusion reaction gradients, microenvironments and quorum sensing. Surface design, cell immobilization and reactor types are all parts of engineering techniques. We then focus on three practical contributions, namely continuous processing, bio-preservation and functional food production. We also handle real-world issues including scale-up, fouling, cleaning-in-place and process control. Overall, altering our perspective on biofilms from issue to platform provides a realistic pathway to more efficient and scalable food fermentation.