Dredge fish in the plate of cornstarch and ensure that all sides are coated in cornstarch. Pat off any excess cornstarch.
Dip each chunk of fish individually in the batter, allow coating to drip, and gently place in oil.
Repeat process for 1/4 to 1/3 of the fish, careful not to crowd the fish.
Cook until lightly browned, stirring occasionally with spider to make sure the pieces of fish do not stick together.
Remove pieces of fish to a rimmed baking sheet with a wire rack.
Season fish with salt. Place baking sheet in an oven or toaster oven at 225F to keep warm.
Lightly heat tortilla over a low flame directly on the burner. When you just start to smell a char, flip. Repeat on the other side.
Assemble tacos with with Mexican crema, cilantro sauce, coleslaw, and pickled onions. You can substitute Mexican crema with Toum. Top with fish.