Put the water in a small saucepan and bring to a simmer. Add the chicken, capsicums and spring onion. Stir in the paprika, cayenne and garlic chilli sauce. Cook gently until the chicken is no longer pink at the centre, then remove from heat.
Slice the baguette lengthways then cut into three equal portions. Butter if you want.
In a mixing bowl combine the chicken mixture and mayonnaise. Use to fill the baguette and sprinkle with chives.