Add the oil and butter to a skillet over medium-high heat. Once the butter has melted, add the mushrooms and onions.
Sauté until the mushrooms have released their water, it cooks off, and the mushrooms and onions are nicely seared (about 10-12 minutes).
Reduce the heat to medium and stir in the garlic, Dijon mustard, Italian seasoning, and lemon juice. Cook for about 30 seconds.
Stir in the white wine and let it bubble for about 30 seconds - 1 minute.
Pour in the cream and cook for another 3-5 minutes or until the sauce has thickened to your liking.
Season with salt & pepper to taste (I am fairly generous with cream sauces) and stir in the chopped parsley. Serve immediately.
Notes
Nutritional information is provided as a courtesy only and should be construed as an estimate rather than a guarantee. Ingredients can vary and Salt & Lavender makes no guarantees to the accuracy of this information.