In a pressure cooker add goat or lamb ribs (margandam) meat, 1/2 of the cut onion, 1/2 of cut tomato, turmeric powder, a cup of water, salt to taste and cook for 3 whistle and keep aside until the pressure is released.
In the mean time heat oil, add black pepper, rest of the cut onion, rest of cut tomato ginger, garlic and sauté until onion , garlic change color (golden brown). Remove from heat cool down and grind this to a fine paste by adding little water as possible.
Add the ground paste to to the cooked rib meat, add water as needed ( 2 cups ) and cook for another 2 to 3 whistle. Remove from heat and Keep aside for the pressure to be released.
In a pan heat oil, add mustard seed, black gram and wait until it start to splatter. Now add the curry leaves cook for few minutes. Add this to the soup in pressure cooker. Mix well, garnish with coriander leaves and serve.
Add chili power or more black pepper to adjust the spice level.