In the mess hall, you can use food resources to have the chef on duty cook up a special meal for their allies, potentially boosting their stats for the next battle! Higher level mess halls will increase the number of allies it boosts, with level 3 feeding your entire army.
Different ingredients will give boosts to different stats. Each ingredient gives +1 to a stat, with a limit of +2 per stat. This can be immensely helpful if you are having a bit difficulty through a battle. Only one meal will go into effect per battle, so if you make another meal, it will overwrite the effects of the previous meal.
Every chef will have their own personal flair when cooking that gives an extra taste (whether it’s savory or revolting) and effect to the dish. This can provide boosts to more stats, negate any boost the dish normally gives, or even reduce your stats! Try to keep track of who is the best chef in the army.