The secret to really flavourful mushrooms is to dry-fry them first. Heat an empty pan and cook the mushrooms until they release all their water and it evaporates. That really intensifies their flavour and improves the texture.
Only then add a knob of butter or some oil, a splash of Marsala or Madeira (they’re perfect with mushrooms) and some herbs. Perfect mushrooms on toast. If you’re feeling naughty, stir in some crème fraîche at the end.