Dry-roast the fenugreek seeds until they darken slightly to a reddish hue.
In a tiny bit of oil, fry the red chilies. Remove, and use a paper towel to absorb the excess oil.
In a spice grinder, powder the fenugreek and chili peppers along with about ½ tsp of salt. Set aside.
Heat remaining oil and add the mustard, asafetida, chilies, chana dal and urad dal. Fry for a minute, then add the peanuts.
Once the peanuts start browning, add the tamarind sauce, the chili-fenugreek powder, and check seasoning. Add more salt if needed.
Let the tamarind sauce reduce on a low flame until it has thickened to a consistency almost like that of molasses (it'll even look a little like molasses with the dals and peanuts suspended in it, but won't be as sticky)
This sauce will store for weeks if kept in the refrigerator in an airtight container.