Soak the rice and the urad dal for 4-5 hours. Together is fine.
Prepare the podi by dry-roasting all the ingredients except the salt just until fragrant. Powder in a spice grinder, add salt and set aside.
Wash the kalyana murungai leaves, and remove the stalks and veins from each leaf. This is important, as these will not grind well and produce an overly fibrous dough.
Drain the rice and the urad dal almost completely. Grind the prepped leaves with the rice and urad dal—adding no additional water. You want a dough at the end of this, not a batter. If you need to, you can sprinkle a little rice flour to bring it together into a tight dough ball.
Add the siththirathai, athimaduram and val milagu powder, and salt to taste. Mix well.
Now make small lime-sized balls of the dough and set aside.
Heat oil in a heavy pan and while it’s heating, start patting the dough balls into small patties. Don’t make them too thin; they should be just smaller than the palm of your hand. You can use a wet cloth to get these ready or an oiled banana or other edible leaf. Avoid using plastic!
Once the oil is hot enough, slip the patties one at a time into the hot oil. They will sink to the bottom, but slowly start to rise. Use a slotted spoon to keep them immersed, coaxing them to puff. Once they’ve puffed and are floating—flip them to cook the other side.
And once they’re turning just slightly golden, you can lift them out and set them on paper towels to absorb any excess oil.
Repeat this process with all the remaining patties.
Arrange the warm vadais on a plate and sprinkle each with the podi prepared earlier. You can store any remaining podi for subsequent use (or substitute for your regular chutney podi or idli podi).