Soak the walnut in some warm water for sometime to soften them. Then blend along with yoghurt, green chillies, garlic and salt to a smooth paste. Check the consistency. It should not be too thick or too watery.
Transfer to a serving bowl and add the lime juice. Mix well. Heat oil in a pan and temper with mustard seeds. After it stops spluttering add the urad dal and curry leaves.
Saute for a few seconds and switch off the flame. Pour this tempering on the chutney and mix well.
