Finely chop the onion, tomato and cut the liver into small pieces.
In a pan heat the oil and temper the mustard and curry leaves. Add onion and saute it until it turns golden brown.
Add tomato and mix well.
Add ginger garlic paste and mix well until the raw smell goes out.
Add red chilli powder, turmeric powder, salt, garam masala and pepper and mix well.
Add mutton liver and mix well. Allow to cook in medium flame for 5 minutes.
Add little water to boil the liver.
Once the liver gets boiled, dry the water and allow to fry for 5 minutes in a low flame to get the masala mixed well with liver. Cook the liver well.
Now mutton liver pepper fry is ready.