Rinse out then soak the two lentils together for at least 5 hours, preferably overnight.
Wash and sieve out as much of the peels as you can, they will mostly float to the top when you rub the grains. You might not be able to get out all the peels, but that's absolutely ok. Even if some remain, it's fine, that will make you bhajias/fritters even crispier. Wash and change the water several times until you're satisfied that the grains are clean and the water is clear. Remember to check for stones that will sink down to the bottom of the bowl during washing if you bought the freshly weighed-out variety.
To check for stones, fill Bowl 1 with the soaked grains and cover with water, then take a Bowl 2. Now gently with a side to side swishing motion, pour the grains with their water into the second bowl. Whenever the water starts reducing such that you can see the grains of Bowl 1, spill the water back from Bowl 2 into Bowl 1 and repeat with the swishing until all the grains have been swished into the Bowl 2. Be careful near the end, to check what is remaining in the bowl because if there are any stones, this technique will help sink them to the bottom of Bowl 1. So you can just scoop them out and chuck them. Repeat a second time just to be sure, you certainly wouldn't want some nasty stones in your yummy bhajias/fritters!
Put the cleaned and drained lentils in a colander to drip out all the water, then add the roughly chopped onion, coriander stems (save the leaves for later), and green chillies.
Now using a food processor, grind these together to make a rough mixture. Do not add water whilst doing this unless you absolutely have to, and then also just add a tsp at a time until you can grind the mixture!
Turn the mixture into a bowl and add the garlic paste and salt. Mix thoroughly, then just before frying add the chopped coriander leaves and some chopped methi (fenugreek).
Heat oil in a deep pan and then pick small balls of the batter using your fingertips and gently drop them into the hot oil. Deep fry on medium heat until golden brown and crispy. Drain well on tissue and serve hot.