For preparing Thakkali Ulli Chammanthi, first heat some Oil in a Cheenachatti/Frying Pan and add Red Chilli, Bengal Gram, some Curry leaves, Asafoetida and Black Gram into this hot oil and roast these ingredients well.
When the Red Chilli, Red/Bengal Gram, curry leaves, asafoetida and Black Gram are roasted properly, add the Tomato and Onion/Shallot pieces and stir it further.
When colour of these ingredients turns into golden, put off the stove and allow to cool the ingredients for some time and then grind it in a Mixer/Grinding stone, along with required quantity of salt, without adding water.
Heat some oil in a Cheenachatti/Frying pan and burst the mustard seeds in this hot oil and also fry some Red Chilli pieces and Curry leaves and add them into the Chammanthi. Serve with Idly/Dosa/Uppuma etc.