Boil the cabbage in salted water for few minutes or until tender. Remove water and keep aside. Add grated coconut, green chilies to the cabbage and mix well. Heat oil in a pan, fry mustard seeds along with cabbage mixture for some time. Remove and keep aside Mix flour with salt and knead to smooth dough using water. Make small balls from the dough and roll into thin chapathis. Place the cabbage curry in the center of it, spread the curry and cover with another chapathi. Paste the edges with water. Fry on a pan until golden brown on both sides. Repeat for other balls and serve hot.