Wash and clean the vanpayar. Pressure cook vanpayar in 2 - 2 1/2 cups water ( I cook it in high flame for 4-5 whistles and keep it closed for 20 minutes. After 20 minutes, open the cooker and drain the water completely).
Grind together small onion,garlic, black pepper, red chilli and curry leaves (It will be great, if you can crush it using mortar & pestle). Heat oil in a pan and splutter mustard. Add ground masala, turmeric powder and curry leaves & fry it for 1-2 minutes.
Add cooked payar & salt. Mix everything well. Add around 1/4 cup (or less) of water & combine. Cook till the water is dried.
Serve hot with kanji or rice.
Notes
As you can see in the picture, I like payar to be mashed and soft. If you dont want it to be pasty, adjust the cooking time accordingly and also adjust the quantity of water that you add to the cooked payar.