Cook mango pieces with some water until cooked through and tender.
Add jaggery and sugar, mix well and bring the mixture to a boil. Lower the heat and simmer until the mixture thickens, about 4~5 minutes. Remove from heat.
Heat 1tsp oil in a small saucepan, add the mustard seeds and green chilies. Once the seeds start to splutter, add the oil to the mango mixture and mix well. Enjoy!!