Cookies are consumable items that decrease hunger. You can find them on the first island, and because of how filling they are, can be vital for surviving the first few days. Note that both insect parts and berries are a more efficient food (per weight), but cookies are the third most efficient food in the game. Making cookies requires using dough with Cacao powder (cacao fruit + stone), and then baking the resulting chocolate dough over a fire. You can also obtain them by trading 5 branches with the Weed Grandpa on the fourth island of Adventure mode.