Peel the sweet potatoes and cut in to fine slices. Place them in a pan of salted water and boil until tender. Once boiled, drain the water and return the potatoes to the pan. Dry them out over a low heat then add the butter and mash the potatoes. Season to taste.
Skin and bone the fish if necessary then cut in to 1cm cubes. Place the chopped fish in a bowl and squeeze over the lime juice. Add the balsamic vinegar and stir gently.
Peel the red pepper and the red onion. Cut both in to fine strips and then mix in to the fish. Stir the fish and the vegetables, making sure they are thoroughly mixed with the lime - this will allow the lime juice and the vinegar to 'cook' the fish. Once the fish has turned white, add the chopped coriander.
Use stainless steel serving rings to plate the mashed sweet potatoes. Remove the serving rings and serve the ceviche around the potato. Finish with some seasoned rocket leaves.
«Make sure to add the coriander leaves at the last minute, if you add them too early they will brown and lose their flavour.»