Pressure cook the soaked horse gram in 3 cups water for 10-12 minutes on a low flame after the first whistle. Set aside to cool.
Drain the water and keep aside. Grind 3-4 tbsp. of the boiled Horse gram lentils to a smooth paste. Keep aside.
Heat oil in a pan and temper with mustard seeds, cumin seeds and fenugreek seeds. After it stops spluttering, add the red chilies, green chilies and curry leaves. Saute for a few seconds.
Add the garlic, cumin powder and pepper powder. Saute for a few seconds more. Then add the stock, salt, tamarind water, sugar and the lentil paste.
