Minced fish ceviche on tostadas

Cut sashimi-quality halibut into roughly one-inch chunks and spread on a small parchment-lined baking sheet.

Freeze until firm enough to mince finely, about 40 minutes.

Grate the carrot. Cut the tomatoes crosswise and gently squeeze out the gelatinous seed section so the chopped tomato is drier, then chop. Chop the serrano chilies.

Grind the firm fish through an electric grinder straight into the bowl of vegetables. Add the lime juice and a sprinkling of salt; adjust the seasoning.

Spoon onto tostadas, top with cilantro leaves and a slice of avocado.