Cooked food is the key to several of Cozy Grove's activities. It can be sold to Mr. Kit for coins, donated to the collection for crafting materials and some completionist serotonin, and, perhaps most importantly, it can be given to pets and imps for essence.
How to Cook Food in Cozy Grove
The system for cooking is a little misleading, but it's actually very simple. To cook something, bring it over to your camp and talk to Flamey. Scroll down to the second to last option: "I want to burn something."
This will open your inventory, where you can select everything you want to feed to Flamey. He'll then cook, smelt or burn whatever you select, returning you the new material.
Different items will produce different materials. Mushrooms will turn into roasted mushrooms, ore will turn into ingots, fish to charred fishbones, and so on. Each has a use somewhere on the island.
To give your cooked ingredients to an imp or pet, put it in your hand and throw it at whatever you hope to feed. The commands are the same as for casting your fishing rod, and characters will similarly chase down whatever you toss provided it's close enough for them to notice it.