Frozen cranberries can be used as well.
If you do not have access to a small grinder, substitute red chilli powder and fenugreek powder in place of methi seeds and green chillies and use only tamarind pulp.
Thokku is best stored in glass or porcelain jars. Avoid aluminium, cast iron, brass for cooking and even stainless steel utensils and plastic for storing to avoid the tamarind from reacting with them.
Keep all containers, spoons and ladles dry. Moisture reduces the shelf life greatly.
Do not skimp on the oil unless you plan to consume it within 2-3 days.
Needs to be refrigerated after a week to keep the oil from going rancid.