Birasta means brown onions. It is an important ingredient used in many type of Biryani to enhance the flavor. The method I have given is traditional method of making Birasta.
Oil for frying
A pinch of salt
Chop Onions into thin slices ad dry them in the sun for consecutive 3 days till the moisture evaporates and the onions become dry.
Then heat Oil in a frying pan on high flame. Once the oil is heated, lower the flame and put onions in the Oil. After the onions changes its colour to golden brown, remove and drain them. Sprinkle some salt over it.
Store Birasta in an airtight container.
Alternatively, the Onions can be dried in Oven by sprinkling some salt and oil over it.