First thing to do is to buy the fresh fish a couple of days before preparing the ceviche, and freeze it (at least this is required by law in Spain if you want to prepare a recipe with raw fish). Then, defrost it the day you prepare the dish

Prepare the dressings. Nothing to do with the corn if you buy it already toasted. Boil the sweet potato for 15-20 min and then cut it in thin slices and set aside

Cut the onion in half, remove the part in the middle (we call it heart in Spain) and put it in the blender glass. Cut the rest of the onion into thin slices and put it in a bowl with cold water to remove the spiciness.

Cut the fish in clean bite squares, put it in a bowl and add 1-2 red fresh chiles cut in very thin slices. Add also a bit of salt. Mix and keep aside (put all the fat and side pieces of the fish in the blender glass together with the onion).

Prepare the "leche de tigre" (tigers' milk): Add a piece of celery to the blender glass (where you had the fish fats and the onion), a minced garlic clove, the juice of the limes and the coriander leaves. Crush in intervals (4-5), just enough to mix it all.

Last step is to assembly everything in a nicely manner! Take a nice bowl and put the fish, add the red onion and strain the "leche the tigre" over. Mix all well with the help of a spoon. Finally, add the dressings, sweet potato and toasted corn. Enjoy it!