Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Once the oil shimmers, add 8 ounces of sliced mushrooms. Cook for 4-5 minutes, stirring occasionally, until they turn golden brown and tender. Add 1 minced garlic clove and sauté for an additional minute, releasing its fragrant aroma. Remove the mushrooms from the pan and set aside.

In the same skillet, pour in 1 cup of chicken broth, scraping up any browned bits from the bottom for extra flavor. Stir in ⅓ cup of heavy cream, ½ teaspoon of thyme, and 1 teaspoon of Dijon mustard. Bring the mixture to a boil over medium heat, allowing the flavors to meld together beautifully while creating a creamy sauce base.

Reduce the heat to low and let the sauce simmer for about 10 minutes. Stir occasionally until the sauce thickens and is velvety, careful to coat the back of a spoon.

Return the sautéed mushrooms to the pan, mixing them into the simmering sauce. Add 1 tablespoon of butter and stir well until melted and fully incorporated. Cook for an additional 2 minutes, ensuring everything is thoroughly heated and combined. Taste the sauce, adjusting seasoning with salt and pepper as needed.