1. Peel the sweet potato, boil it, and cut it into thin slices.
2. Cook the corncob, then peel off the kernels.
3. Finely chop the garlic clove, lime chilli and coriander.
4. Cut the fish into 2 cm cubes, put them in a bowl and season them with salt and pepper.
5. After 1 minute, add the garlic and chili.
6. Pour lime juice over it and add the chopped coriander and ice cubes.
7. Stir and let the fish stand for a few minutes.
8. Cut the onion into rings.
9. Remove the ice cubes and add the onion.
10. Stir everything again and season it to taste. Then serve the Ceviche with corn and sweet potato.