Grate cucumber and carrot and transfer into a deep bowl.
Add the boiled rice and mix mashing them lightly with a spoon. Blanch green peas in sufficient boiling water for two to three minutes. Drain and set aside to cool. Heat oil in a pan, add mustard seeds. When they splutter add asafoetida, curry leavers, ginger and green chillies and sauté for five seconds.
Add this to the rice in the bowl and mix. Add the green peas and salt and mix. Add yogurt and mix well.
Keep it in the refrigerator for atleast five to ten minutes.