I normally use this soft mushy filling for my Cigar-Roll Sandwiches as for those we need a filling that is a bit smooth and not too 'lumpy'.
The filling needs to be soft and not too lumpy, so what I do is, I use my processor to chop everything finely one at a time. If you don't have a food processor, you can just grate the ingredients.
Heat oil or butter, add onion and fry until translucent. Then add the capsicum, fry for a few seconds then add the garlic. Stir well, and add the chicken. Cook until chicken changes color, next add all the rest of the veggies, green chilli, salt and powdered spices.
Keep stirring regularly on low heat, and you can add about a quarter cup of water to help cook everything properly and to prevent it from sticking to the bottom of the pan. Make sure you dry off the water completely though once everything is soft and mushy.
Adjust salt and spices to your taste, sprinkle the chopped coriander and add the fresh lemon juice and soya sauce. Mix well and turn off the heat.
Let the mixture cool completely before using as a filling.