Rinse the rice in water 2-3 times and soak in sufficient quantity of clean water.
Mix the three lentils together, rinse them with water 2-3 times and soak for 5-6 hours.
Drain the soaked dal and rice and grind the rice with the green chillies into a smooth paste. Remove into a big bowl. Add the sour yogurt to this mixture, stir well.
Fermenting: Keep the bowl tightly covered and keep in a warm place overnight. The bowl has to be large enough, because the batter will rise due to fermentation.
To prepare handwo, take the fermented batter. Add the veggies, salt, turmeric, grated ginger. Give the batter a good stir. You can taste at this stage to check for salt and spices. If you want it spicier, you can add some red chilli powder.
Grease a microwave safe round pan. Pour the batter into it. Microwave at 80% power for 12 minutes or until a tester comes out clean. Alternatively you could use a steamer for 15 minutes or so. I used the microwave and it was very fast and came out clean.
Once done, remove and cool for 5 min. Keep a plate to cover the pan, invert the pan so that the cake comes out neatly onto the plate. Cut it into 8 large wedges.
Heat the oil, add the tempering ingredients. Once the sesame seeds turn golden, remove from flame. Garnish the handwo wedges with the tempering. You can even slow roast the handwo slices in this tempered oil until the outer layers turn golden and crispy.