Finely chop one onion and mince two cloves of garlic. Clean and slice the mushrooms uniformly, aiming for about one pound.

Melt four tablespoons of unsalted butter over medium heat. Add the chopped onion and sauté for 5-6 minutes until softened.

Add the sliced mushrooms to the skillet and sauté for 8-10 minutes until they turn golden brown and release their juices.

Pour in one cup of white wine and scrape the bottom of the skillet. Allow the wine to reduce for 3-4 minutes.

Stir in one cup of broth and bring the mixture to a simmer. Cook for 10 minutes to meld flavors.

Lower the heat and mix in one cup of heavy cream and two teaspoons of Dijon mustard. Stir and let it thicken for 5 minutes.

Sprinkle chopped fresh parsley on top and serve the sauce over your favorite proteins or vegetables.