In a large bowl, marinate chicken in vinegar, olive oil, mustard, salt and pepper for about 2 hours.
Drain and reserve marinade. Pan fry chicken until golden brown. Set aside.
Boil reserved marinade in a saucepan and combine pineapple syrup, broth, soy sauce and flour.
Stir mixture and add chicken pieces. Cook until chicken is tender.
Add the snap peas and pineapple chunks.
Remove from heat. Arrange in a platter and top with spring onions. Serve hot.