Slice the chicken breasts in half lengthwise to create four thin cutlets. Season both sides with salt, pepper, and garlic powder. Lightly dredge in flour, shaking off any excess.
Heat olive oil and 1 tablespoon of butter in a large skillet over medium-high heat. Add the chicken and sear for about 4-5 minutes per side until golden brown. Remove and set aside.
In the same skillet, add the remaining butter. Sauté the mushrooms until browned and softened, about 5 minutes. Add the minced garlic and cook for another minute.
Pour in the Marsala wine, scraping up any browned bits from the pan. Let it simmer and reduce by half, about 2-3 minutes.
Lower the heat to medium and stir in the heavy cream. Return the chicken to the skillet, coating it in the sauce. Simmer for another 5 minutes until the sauce thickens and the chicken is cooked through.
Taste and adjust seasoning if needed. Serve hot with mashed potatoes, pasta, or crusty bread.