In a medium fry pan, heat the olive oil over medium-high heat and add the mushrooms, fry until golden, then remove to a bowl and set aside.
1 tablespoon olive oil, 200 g button mushrooms
Turn the pan down to medium heat, then add the onion and bacon (adding more oil if needed), and fry until the onion is translucent, then add garlic and fry for another 30 seconds.
1 small brown onion, 200 g smoked bacon, 3 fresh garlic cloves
Return the mushrooms to the pan, and pour in the wine.
¼ cup dry white wine
Stir to deglaze the pan and scrape up any flavour spots from the base of the pan, then simmer until the wine is almost completely evaporated.
Stir in cream, parmesan cheese, salt and pepper.
300 ml thickened cream, 40 g freshly grated parmesan, ¼ teaspoon cooking salt, ¼ teaspoon freshly ground black pepper
Simmer until slightly thickened (don't forget it will thicken as it cools - see my notes) and serve with extra parmesan on top (if using).