In a large covered skillet, heat olive oil over medium-high heat. Cook chicken in oil until browned on all sides. Remove chicken from skillet.
Arrange potatoes in the skillet to cover the bottom. Scatter garlic cloves over potatoes. Place chicken on top of garlic and potatoes. Sprinkle pepper, salt, and parsley over chicken. Pour sherry and port over all. Cover, and simmer over low heat until potatoes and chicken are cooked through, approximately 45 minutes.