Wash and soak the dals in plenty of water for at least 5 hours. Drain well and grind the dals with the yoghurt to a smooth, batter-like consistency in a food processor. Try not to use any water to loosen the mixture while grinding.

Pour the mixture into a large bowl and mix in the rice flour, chilli powder, turmeric powder, chilli and ginger pastes, grated vegetables, sugar and salt till no lumps remain.

Heat 1 tbsp oil in a pan till quite hot. Add the curry leaves, turn off the heat, pour into the batter and mix well.

Cover and leave the batter to ferment overnight or for 6-7 hours.

Preheat the oven to 180 ℃ and while the oven is heating, pour 2 tbsps oil to coat the bottom of a cast iron skillet, and leave it to heat in the oven.

Gently mix in the soda bicarb into the batter taking care not to overmix.

Once the oven is hot, carefully remove the heated cast iron pan from the oven and pour in the batter and bake for35-40 mins. When the handvo has baked for about 25 mins, heat the remaining oil in a pan and crackle the mustard and sesame seeds. Pour this over the almost-done handvo and brown at 200 ℃ for a further 5 -10 minutes till the top is golden and you get a clean toothpick.