Ensure you use good quality fresh flour. You can also make your own fresh flour at home or you can buy store bought Idiyappam Flour.
If the modak break while pressing and making cup, sprinkle water and ghee, knead well.
You can reduce the jaggery quantity as needed to suit your taste.
For soft outer layer, boil water well for making the dough. Dough should be almost cooked with the hot water so that you get non sticky pliable dough.
Do not over cook , it may give you rubbery and broken kozhukattais.