Oysters on the Half Shell with Ceviche Topping

In a small skillet, toast the coriander seeds over moderate heat until fragrant, about 2 minutes. Let cool, then coarsely crush the seeds in a mortar. In a small bowl, mix the crushed coriander with all of the remaining ingredients except the oysters.

Arrange the oysters on crushed ice. Spoon some of the topping on each one and serve right away, passing additional topping at the table.