When frying croquettes, a mixture of starch and flour is usually added. This is because the combination of these two ingredients provides a strong shell that allows the croquettes to retain their shape during frying.

The usual way of doing this is to mix starch and flour in a ratio of about 2:1, which can also be adjusted to suit individual tastes and needs. Once mixed, add a good amount of salt and pepper, and any other seasonings you like. Pour the mixed batter into the croquettes so that they are evenly coated.

Then, you can start frying the croquettes. When frying the croquettes, pay attention to the temperature of the oil, usually around 180 degrees F. Put the croquettes into the hot oil one by one, and fry them over medium-low heat until they are golden brown, then fish them out to drain the oil and serve them.