Before you begin cooking, ensure all your ingredients are prepped: slice the mushrooms, finely mince the shallot, mince the garlic, and chop the fresh herbs.

Heat olive oil and 1 tablespoon of butter in a large skillet or frying pan over medium-high heat. Once the butter is melted and sizzling, add the sliced mushrooms in a single layer if possible. Cook, stirring occasionally, for 5-7 minutes, or until the mushrooms are deeply browned and have released all their liquid, which has then evaporated. This step is crucial for flavor.

Reduce the heat to medium. Add the remaining 1 tablespoon of butter to the skillet. Once melted, add the minced shallot and cook for 2-3 minutes until softened and translucent. Stir in the minced garlic and cook for another 30 seconds until fragrant, being careful not to burn it.

Sprinkle the all-purpose flour over the mushrooms and aromatics. Stir well with a wooden spoon or spatula for 1 minute, ensuring the flour is fully incorporated and cooked slightly (this creates a roux).

Gradually whisk in the chicken or vegetable broth, a little at a time, to avoid lumps. Continue whisking until the sauce is smooth. Bring the mixture to a gentle simmer and cook for 3-5 minutes, stirring occasionally, until the sauce has thickened slightly.

Reduce the heat to low. Stir in the heavy cream and chopped fresh thyme. Season with salt and freshly ground black pepper. Let the sauce simmer gently for another 2-3 minutes, allowing the flavors to meld and the sauce to warm through. Do not boil vigorously after adding the cream.

Remove the skillet from the heat. Stir in the chopped fresh parsley. Taste the sauce and adjust seasoning as needed.

Serve the Creamy Mushroom Sauce immediately over pasta, chicken, steak, pork, or vegetables. Garnish with additional fresh parsley if desired.