Heat a small pan and add peanuts. You can skip this step of roasting peanuts if you have pre-roasted, skinned peanuts.
On low heat, dry roast the peanuts while stirring continuously till a few black spots appear on them. Keep them aside till they are cooled completely.
Rub roasted peanuts between your palms; the skin comes out easily. Transfer them to a mortar and pestle. Crush the peanuts to a coarse powder.
Chop the cucumbers. Transfer them to a large mixing bowl. Season them with salt, mix, and set aside for 10 minutes.
Squeeze water from the cucumber by cupping them between your palms or holding them in your fist. Or you can tie them to a muslin cloth and squeeze gently to drain out excess liquid. Transfer cucumber to a bowl.
Add chopped green chilli, grated coconut, salt, lemon juice, and sugar to the cucumber. Mix nicely.
Prepare tadka with heating oil. Add mustard seeds, urad dal, and curry leaves. Allow the seeds to pop.
Pour this sizzling tadka over the khamang kakdi. Add crushed peanuts and chopped coriander, and mix nicely.
Khamang Kakdi is ready to serve.