Heat the butter and olive oil in a large skillet over medium heat until hot.
Add the onion and garlic and cook until softened. Next, add the mushrooms and cook until tender. Remove the cooked vegetables from the skillet and set aside.
Add the broth and cream cheese to the skillet. Whisk until the cream cheese has melted. Add the cream, salt, and pepper. Stir until smooth.
Add half of the mushroom back to the pan and puree with an immersion blender until smooth. Sprinkle the xanthan gum on top of the sauce and whisk until smooth. Add the remaining mushrooms back to the sauce and serve.
Notes
Nutrition: the nutrition facts are for ⅛th of the recipe. This is approximately ½ cup. There are 4.4 NET carbs per serving.To Reheat: warm it in a microwave-safe bowl and heat for 1-2 minutes, then stir. Repeat until it's hot. You can also pour it into a saucepan and reheat using low-medium heat. Stir often and heat until hot.