Take your left over rice and mix yogurt into it. Add enough yogurt to give it a paste like consistency. You can add some water or milk as well if the yogurt is very thick.
Add some salt to this paste you have prepared using rice, yogurt, milk and water.
For tempering, heat some oil in a pan. When hot add cumin and mustard seeds along with some asafetida.
Add some chopped ginger, chili and curry leaves. You can skip chili if needed as these are optional. Let these cook well but make sure they do not get burnt. You can lower the gas flame to reduce the heat and keep stirring.
Add the tempering to the rice and yogurt paste we had prepared. Mix them well and your Bagala Bath is ready.