You can vary this dish according to what you have to hand. For instance: Switch the onion for a red onion, for a slightly sweeter flavour.
Use lemon thyme or rosemary instead of thyme – rosemary gives a more Italian flavour.
For a stronger mushroom punch, use shiitake, or a mixture of mushrooms.
If you are a blue cheese fan, switch the cheese for crumbled Stilton, Roquefort or Gorgonzola.