I recently introduced a vegan friend to flats (button mushrooms that have been allowed to grow up, and are about 15cm across) cooked slowly with a little olive oil under them till the cup fills with juice. The expression of astonished pleasure…
Soaked dried mushrooms are ok; I use them in risotto; but I soak them in hot water and when it's cooled to warm I chop the formerly dried mushrooms into little slivers.