Wash and soak chana overnight.
Cook chana and potatoes in pressure cooker till they become mashable but not soggy. Add a little water and salt in chana before cooking it. (I cook chana on medium-high heat till the first whistle. Then reduce the heat to low and cook till 3 more whistles. I keep potatoes in a separate container in the same cooker.)
While the chana and potatoes are cooking, heat a pan and add oil in it.
Add cumin seeds (jeera). When they start to splutter, add chopped onion and sauté for a minute.
Add grated ginger and sauté for couple of minutes. Add turmeric powder and sauté for aother minute, then turn off heat.
After chana and potoes are cooked, mash potatoes, and mash or coarsely grind chana in a mixer. (Chana needs to be piping hot if you want to mash it.)
Add ground/mashed chana, mashed potatoes, and sautéed onion to a large mixing bowl.
Add red chili powder, garam masala powder, salt, lemon juice, chopped green chilies, and chopped coriander.
Mix to make a dough, then grease your palm with oil and shape patties in the shape of your choice. (I made ball-shaped patties, which I cooked in appam pan. I also made some rectangular shaped ones, which I cooked on a flat pan.)
Coat al patties with lightly roasted rava.
Heat an appam pan, add oil in each section, then add the patties starting from outermost ring first. (Patties in the middle of the pan get cooked first, ones outside take longer time.)
Cook on medium-high heat till they turn golden brown, then turn them over one-by-one. (Keep checking the patties every 5 minutes to see if the're done or not. Else, they'll get burnt.)
Add a little oil from the sides after turning them over. (Rava tend to get quite dry when cooking with less oil, so you'll need to add a little oil.)
Cook this side too till it becomes golden brown, then transfer them onto a plate.
Serve with tomato ketchup or green chutney.