Heat the butter and oil in a large pan or skillet over medium-high heat.
Sauté the onion until softened (about 3 minutes).
Add the mushrooms and cook for about 4-5 minutes until golden and crispy on the edges.
Pour in the wine and cook for 2 minutes, to reduce slightly.
Stir through thyme, 1 tablespoon of parsley and garlic. Cook for a further 30 seconds, until fragrant.
Season generously with salt and pepper (to your taste).
Sprinkle with remaining parsley and serve warm.