Pat the chicken dry and season lightly with salt and pepper if desired.
Heat 2 tablespoons olive oil in a large skillet over medium-high heat.
Add the chicken to the hot skillet and cook 3–5 minutes per side, until cooked through; remove to a plate and set aside.
Add the sliced mushrooms and minced garlic to the skillet and cook a few minutes until the mushrooms are tender; remove and set aside with the chicken.
Reduce heat to medium and pour in 1 cup chicken broth, then add 1/2 cup heavy cream, 2 ounces softened cream cheese, 1 teaspoon garlic powder, 1/2 teaspoon salt, and 1/4 teaspoon pepper; whisk until smooth.
Whisk in 1 tablespoon all-purpose flour until incorporated and cook 1–2 minutes more, stirring, until the sauce thickens slightly.
Return the cooked mushrooms and garlic to the sauce, then add the chicken back to the skillet and spoon the sauce over to coat; heat for a couple of minutes to warm through.
Serve immediately with the creamy mushroom sauce.