Sorry I should have said it better. To be able to add food to the stew in first place you indeed need 2 brown mushrooms in bin. Before it says adding food to stew. Before that if you have less or 0 will tell you not enough food to do this. And you can also collected mushrooms and collectibles when game is on pause. I think pretty boring doing it that way. But sometimes you need to do it to gather food before you get the tech levels you need to keep your village going.