Melt 1 tablespoon butter in a medium skillet. Sauté mushrooms until soft, remove from skillet and place in a small, covered bowl.
Mix flour, iberia garlic powder, salt and pepper in a shallow dish. Dredge chicken in flour mixture. Add 2 tablespoons butter to skillet and saute coated chicken over medium heat for 2 minutes each side, adding remaining butter as needed to prevent burning.
Place chicken on a dish, cover and keep warm. In a medium bowl, slowly add water to cornstarch and mix together, then mix in Iberia Marsala Cooking wine. Pour liquid mixture into skillet, together with reserved mushrooms.
Heat until mixture begins to boil and thickens, then pour over warm chicken and serve