Dry roast the black-eyed peas till it exudes the smell of the beans. The beans dont need to get browned. Add about 1/4 cup of water to the roasted beans and cook them till done. I cooked them in the pressure cooker (one whistle). Take care that they dont become mushy.
Add the oil into a pan. Once hot, sputter the mustard and redden the urad dal. Then add the green chillies, ginger, curry leaves and hing. When the ginger softens (test with the spoon you will be using to stir the pan), add 4.5 to 5 cups of water and let it come to a boil. Then add enough salt to the water (water should taste salty) and stir in the roasted rice flour. Add more water to incorporate all the flour. Stirring the mixture is important to prevent lumps. Then add the cooked black-eyed peas and coconut gratings and keep stirring. You cannot walk away from this pan, you have to keep stirring. The mixture would turn into a single mass around the spoon within a few minutes. Let the mixture cool to handle. Then form round disks (cakes) about 1/2 inch thick, make a hole in the centre with your finger and steam it for about 10 minutes. I steamed them in an idli steamer. To check whether the cakes have steamed well, insert a clean spoon into a cake and it has out come out clean.
These cakes are usually served with home-made butter. But I would not load up on all that fat. I think they would go well with any chutney, pickle or sambar. As for me, I would like mine plain.
Tip: Use non-stick pan for roasting and preparation of the dish to ensure uniform distribution of heat while roasting and usage of less oil (fat).
Source: Cook & See Part 1 (Samaithu Paar) by S. Meenakshi Ammal
Reference: Patti (my grandmother) - Dad's mother