Lightly roast the dal until it's barely browning and fragrant.
Then soak the roasted lentils for a minimum of 3-4 hours, or until you can pinch one through and break it without any effort. Drain completely.
Transfer to a food processor or blender and pulse until you have a smoothish paste. You may need to scrape the sides down a few times to achieve a consistent texture.
Now heat a heavy bottomed pan and add a few tablespoons of sesame oil to it. Before the oil is too hot, transfer the chana dal paste to it, lower the heat, and start mixing: press-scrape-turn, over and over, exposing every inch of the soaked gram to heat little-by-little so that it all cooks evenly.
Don't be afraid to scrape the bottom of the pan with full vigor. Use a metal spatula, if it helps.
Add a few more spoonfuls of oil, one spoonful at a time, if the mixture sticks too much to the bottom of the pan. I used about 1/4 cup in total, but you might be able to get away with less.
Do all this on low heat, taking your time over it.
On the side, set the cup of jaggery to heat with a little water. Allow it to come to a bubble. There's no need to work towards a 1 or 2-string consistency; what you need is a thickish syrup.
Get the flavorings ready: a pinch of edible camphor, some cardamom pods. You can also add a 1/2 teaspoon of dry ginger, if you like. Crush these together well and add them to the jaggery syrup.
When the okkarai is deepens in color and is starting to look a little less raw, much less pasty and a lot more crumbly, add the jaggery syrup, and continue thecchufying, pressing-scraping-turning to incorporate and then to ensure that any residual moisture evaporates.
Continue cooking until the okkarai once again is starting to look slightly like a crumbly halva. The sugars in this will be hot and therefore somewhat liquidy; the mixture will become even more crumbly as it cools--so don't overcook it at this stage.
Once the okkarai has cooled, it should "udirify" or fall apart in crumbles. It should hold together briefly like a laddoo but then easily crumble apart. That's its signature texture.
At this stage, you can add what nuts and flavorings you please: cashews are typical, as are small bits of coconut. I added wild almonds and a little powdered panam-kalkandu or palm sugar jaggery to give my okkarai a light gaund-ki-laddoo-like crunch.
Toast the nuts in a small bit of sesame oil (or ghee, if you absolutely must), and mix in.
Okkarai should store at room temperature for several days or in the fridge for longer