In a large covered frypan, heat olive oil over medium-high heat. Cook chicken in oil until browned on all sides. Remove chicken from frypan.
Arrange potatoes in the frypan 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.