Make the dough: put the rice flour, urad dal flour, besan, sesame seeds, cumin, red chilli powder, asafoetida, curry leaves and salt in a wide bowl and mix well. Rub in the melted butter until the flour looks like coarse crumbs — this is what makes the thattai crisp rather than hard.

Add the drained chana dal (and the peanuts, if using), then sprinkle in water a spoonful at a time and knead into a stiff, smooth dough that holds together without cracking. It should be firmer than a chapati dough; a soft dough drinks oil and fries up limp. Cover and rest for 10 minutes.

Divide the dough into about 20 small balls, roughly the size of a large gooseberry, and keep them covered with a damp cloth so they do not dry out.

Press the discs: grease a thick plastic sheet, a zip-lock bag cut open, or a piece of banana leaf with a little oil. Place a ball on it, cover with another greased sheet, and press down evenly with the flat base of a bowl or your palm into a thin round disc of about 2 to 2.5 inches. The edges may crack a little — that is normal and even pretty. Prick each disc in two or three places with a fork so it does not puff up like a poori in the oil.

Heat oil in a kadai on medium heat. Test with a tiny piece of dough — it should rise steadily, sizzling gently, not shoot up and brown at once.

Slide the pressed discs in, a few at a time without crowding, peeling each one carefully off the sheet. Fry for 1 to 2 minutes until the sizzling calms, then flip and fry the other side until the discs are deep golden and completely crisp. If they colour too fast, lower the heat — the centres need time to cook through.

Drain on kitchen paper and leave to cool completely; thattai crisp up fully only as they cool, so resist judging the first one while it is still warm.

Once cold, store in an airtight tin at room temperature — they keep crisp for 2 to 3 weeks, if they last that long.