Place the chicken cubes in a round dish and add the onion seeds, ginger, garlic, chilli powder, turmeric, salt and coriander powder.
Mix the spices into the chicken and add half the mango slices to this mixture as well.
In a medium saucepan, heat up the oil and fry the sliced onions until golden brown.
Add the curry leaves.
Gradually add the chicken pieces, stirring all the time.
Pour in the water, lower the heat up and prepare for about 12-15 minutes, stirring occasionally, until the chicken is cooked through and the water has been absorbed.
Add the remaining mango slices, tomatoes, green chillies and fresh coriander and serve hot.