Cut the chicken into 2cm pieces. Combine the oil and spice mix in a large bowl. Add the chicken and oregano. Stir to coat. Thread chicken onto 8 skewers. Cover and refrigerate while making the saute chilli mango.
Pour sugar into a non-stick frying pan. Place over medium-high heat, stirring occasionally until melted and deep golden colour. Remove from heat, add combined lime juice, fish sauce and water (be careful mixture may spit). Return to heat and cook, stirring over medium heat until the toffee dissolves and syrup is smooth. Bring to the boil, boil gently 5-8 minutes until syrup thickens, stir in the chilli. Add the mango and toss gently until mango well coated. Remove from the heat, scatter over the green shallots.
Preheat barbecue plate or grill over medium high heat until hot. Barbecue chicken skewers, 10 minutes, turning often until cooked through. Serve with saute chilli mango.