Step 1Place the chana dal, urad dal, toor dal and cumin seeds in a small skillet and toast over medium-high heat until the dals turn a few shades darker and release their aroma, about 2 minutes. Cool to room temperature.
Step 2Heat the oil in a skillet over low heat and add the coriander seeds, fenugreek seeds, chiles and asafetida. Stir constantly until the spices release their aromas and turn brown, 1 minute. Turn off the heat and cool to room temperature.
Step 3Grind the spices and dals to a coarse powder and store in an airtight, clean and dry jar away from direct light and heat. This mixture should keep its potency for at least 6 months.