Since the update that introduced the Cauldron and the Ladle, players can create custom Stews. These differ from regular foods because they use a Clay Bowl and have a maximum of 10 portions. Stews are created with water and any number of edible items. The stat values of the items added are averaged into the final stew. The color and name of the stew is determined by the last item added into the stew.
To make a custom Stew, you have to make a Cauldron, then fill it with water by clicking on it with a water container. It will take 5 portions of your water container. Drop as many edible items as you want into the Cauldron. After that, use a Ladle to scoop the stew out of the Cauldron, then click the Ladle onto a Clay Bowl to pour the Stew into the bowl. The amount of stew in the Ladle determines the portions of the stew.