Heat the oil in a small pan for the tempering, when the oil is hot, lower the heat and add the urad dal and mustard seeds. Allow the seeds pop and splutter. Reduce the heat to low and add asafoetida, and curry leaves, and saute for a minute until the urad dal turns light brown.Take it off the heat, and pour the tempering over the chutney. Mix well. Enjoy with dosa!