Cebiche is not a dish eaten very cold; it tastes better when the ingredients are room temperature, so don't worry about chilling the ingredients or the plates it's served on. Choclo corn is a Peruvian variety with very large kernels, often sold boiled and frozen. Cancha corn is a kind of toasted corn similar to corn nuts. You can buy both types of corn in some larger supermarkets and in grocery stores catering to Peruvian or South American customers, or find them online.