Chop all the vegetables and keep them ready. Make sure to keep the chopped potatoes in water to avoid them from turning brown.
Heat a small pan, dry roast rice and moong dal separately, until they turn aromatic. Make sure they do not turn brown. Transfer these to a bowl and wash thoroughly. Drain and set aside.
In a pressure cooker, heat 2 tsps oil. Once it turns hot, add mustard and cumin seeds, let them splutter. Next add urad dal, chana dal and let them turn light brown. Now add green chillies, curry leaves and turmeric. Let the colour of green chillies change slightly.
Next add chopped onions and saute until they turn light brown. Now add chopped tomatoes and saute until they turn soft but not mushy.
Once the above step is done, put in all the other finely chopped vegetables. Give a good mix and add roasted and washed rice and dal. Add water, salt as per taste, some fresh grated coconut and lemon juice. Mix thoroughly. Close the lid of the pressure cooker along with the whistle and cook upto 2 whistles.
Let the pressure release on its own and then remove the lid. You should be able to see moong dal and rice completely in their shape without breaking. Fluff up the cooked Akki Usli gently without breaking the rice or lentil. Serve hot with more coconut, chopped coriander leaves and lemon juice (optional).