Soak 1 cup idli rice, 1/4 cup urad dal, and 1 tsp fenugreek seeds separately for 4 to 6 hours
Grind urad dal and fenugreek seeds to a smooth batter
Grind idli rice to a slightly coarse batter
Mix both batters with salt
Ferment the batter overnight or until doubled in volume
Grease idli molds with oil
Pour batter into molds
Steam for 10 to 12 minutes
Remove idlis and keep aside
Soak 1/2 cup toor dal for 20 to 30 minutes
Pressure cook toor dal with turmeric and water until soft
Mash the cooked dal
Heat oil in a pan
Add mustard seeds, cumin seeds, curry leaves, dried red chilies, and asafoetida
Add chopped onions, tomatoes, green chilies, and drumsticks or mixed vegetables
Cook until soft
Add sambar powder, turmeric, and salt
Add tamarind extract and water
Simmer until vegetables are cooked
Add mashed dal
Adjust consistency with water
Add jaggery if needed
Finish with coriander leaves
Serve hot idlis with sambar