Every so often a glint appears in the grass, somewhere your villagers can see. Click it. Resources go straight to your stores, and mushrooms go into your foraging bag. Open the bag and you get a picnic cloth with everything you have found lying on it. Drag a mushroom out of the bag and drop it on a villager, and it works on that one person. Every species has its own effect, and none of them carry a penalty.
Chanterelle: double walking speed
Orange bolete: double work speed
Porcini: double materials carried, in the same time
Hedgehog mushroom: everyone within 15 m gains the XP he earns
Morel: everyone within 15 m shares his buffs
Funnel cap: immune to every debuff for a full day
Fly agaric: works straight through the night, no sleep
Witch's bolete: double XP
Tinder bracket: adds 3h to every buff already running
Birch bolete: doubles the strength of every buff already running
Every species also has a large variant that hits harder and lasts longer, tripling instead of doubling.
A villager can carry four buffs at once. Stack multiple together to get the most out of your mushrooms!