Heat 1 tablespoon of oil in a frypan. Cook onion and garlic until softened. Remove from heat.
Peel and slice mangoes, reserving any remaining flesh for the sauce.
Flatten chicken slightly. Sprinkle pepper over. Spread onion and garlic evenly inside chicken. Arrange mango slices over onion and garlic. Fold one side of chicken breast over to enclose filling. Secure with toothpicks.
Cook fillets in remaining oil for at least 5 minutes on each side.
Combine sauce ingredients in a small pan (mango, honey garlic and coriander). Add a little stock or water. Cook until slightly thickened. Pour sauce over cooked chicken.