Heat refine oil in a kadai.

Fry fish pieces and potato pieces.

Now take a Kadai and heat 3tablespoons mustard oil.

Now fry onion,green chillie,ginger and garlic paste.

Now add all spices.

When masala is frying properly add water.

Now add sugar and salt as per taste.

Now fry the mixture until the oil get separated.

Now add fish and potato pieces.

Cover with lid,

Now add garam masala.

The curry is ready to serve.