Mix the spice mix together and set aside.
The fish should be dry. Use a paper towel to blot it if necessary
Mix half the cornstarch and half the spice mix on a paper plate.
Dredge the pieces of fish through the mix, shake the excess off and arrange on a plate.
Replenish the mix as necessary. If you have any spice mix left over you can dust the pieces with it before or after frying.
Heat oil in a heavy bottom skillet until shimmering. Add the fish in batches and fry for a about two minutes on each side. The color of the fish changes as it cooks and it should release easily when it's time to turn.
Drain on paper towels.
Squeeze the lime juice over top of the fish and garnish with freshly chopped parsley or cilantro before serving.