Cook until the shallots are soft and the mushrooms have released their juices.
Usually, mushrooms release so much water that keeping the pan moist isn't the problem; evaporating all the liquid is.
Sauté until mushrooms release their liquid, liquid evaporates and mushrooms begin to brown, about 10 minutes.
Add mushrooms, and sauté, stirring frequently, until mushrooms soften and begin to release their liquid, 8 to 10 minutes.
Add the mushrooms and cook, stirring often, until the onions are soft and the mushrooms have released their juices, about 8 minutes.
Season with salt and pepper and cook, stirring frequently, until the mushrooms have released all their liquid and are lightly browned, 10 to 12 minutes.
The mushrooms then release much of their water, which can be allowed to boil off or be poured off and used as a stock.
After a minute, mushrooms should release some liquid; if not, add a tablespoon or two of water or stock.
Add to shallots with oregano and cook a few minutes, until mushrooms release their liquid and are cooked.
An elevated mushroom will more easily release its spores into wind currents or onto passing animals.