Wash the mushrooms and dry well on a towel. Cut them into pieces of roughly equal size optional). In a deep nonstick pan, warm the butter and oil and sautee the onions for 4-5 minutes, stirring constantly.
Add the mushrooms and continue sauteeing for 8 minutes until the liquid evaporates. Add the salt, pepper and garlic, then add the wine. Finally, add the stock cube or homemade vegetable stock.
Simmer until the wine has evaporated, and only the oil remains. Then add the parsley or thyme and mix. Simmer for 1-2 minutes. Serve immediately.