How to check if oil is ready - tear a pinch of dough and drop it into the hot oil. If it immediately floats on the surface, then oil is ready. If it is still at the bottom of the kadhai and coming slowly to the surface of oil, then oil is not ready, it will take another 5 more minute. You need to do this thing many times to adjust the heat of the oil in order to get perfectly puffed up luchi.