A thokku is a pickle in which the main ingredient being pickled (Indian style), is usually sliced thin or grated and cooked along with spices till thick so the oil floats up. This means that the moisture content is greatly reduced and also contributes to the shelf-life of the pickle.
A ginger pickle is somewhat a contradiction of terms. Ginger is already fiery without pickling it! Use young and very tender ginger to make this pickle . The addition of a bit of jaggery balances out the spicyness to make a very nice pickle. Here is how I make it.