Put sesame seeds on a strainer and wash it under running tap.
Dry roast the sesame seeds in a pan over low heat for 2–3 minutes until they begin to pop and release a nutty aroma. Let them cool slightly.
In a grinder or mortar and pestle, combine roasted sesame seeds, onion, garlic, ginger, green chilli, and salt.
Grind everything together into a coarse paste. Do not add water at all. The onion will release its juices.
Taste and adjust salt or spice levels as desired.
Serve fresh as a side chutney. Can be stored in an airtight container for up to 5 days in the refrigerator.