Cook toor dal: Wash 1 cup toor dal. Pressure cook with 2.5 cups water and half tsp turmeric for 4 whistles. Mash completely smooth.
Soak tamarind: Soak a lemon-sized tamarind in 1.5 cups warm water. Extract and strain.
Prepare vegetables: Use pearl onions (shallots whole), 4-5 drumstick pieces and 2 large ripe tomatoes — the classic kalyana sambar combination.
Make fresh sambar masala: Dry roast 2 tbsp coriander seeds, 1 tsp cumin, 1 tsp black peppercorns, 4 dried red chillies, 2 tbsp chana dal and 2 tbsp fresh grated coconut for 5 minutes. Grind to a smooth paste with water.
Cook vegetables in tamarind: Add tamarind water, pearl onions, drumstick and tomatoes with half tsp turmeric, 1 tsp red chilli powder and salt. Boil 12 minutes.
Add mashed dal: Add mashed toor dal and stir well.
Add fresh masala paste: Add the freshly ground sambar masala. Stir thoroughly and add water to adjust consistency.
Simmer: Cook on medium heat 10-12 minutes until thick and well-blended.
Make generous tempering: Heat 3 tbsp ghee. Add 1 tsp mustard seeds. When they pop add half tsp fenugreek, a generous pinch of asafoetida, 2 dried red chillies and curry leaves. Add 8 sliced shallots and fry golden. Pour over sambar.
Serve: Adjust salt. Kalyana sambar (wedding sambar) is made in large quantities with fresh-ground masala and extra ghee tempering. Serve with steamed rice, idli or dosa.