Put fish in a shallow baking dish, pour milk over it, and chill, covered, turning over once, 30 minutes. In case you were wondering, soaking fish in milk helps to get rid of the fishy smell/taste (and this goes without saying, but a milk bath is no substitute for fresh fish).

Meanwhile, stir together pistachios and cornmeal in a shallow bowl.

Remove fish from milk, letting excess drip off. Transfer to a plate and sprinkle all over with s&p, then dredge lightly in cornmeal-pistachio mixture. Transfer to a clean plate.

Heat oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then cook fish, turning over once, until golden and just cooked through, about 6 to 8 minutes total.

While fish cooks, stir together all ingredients for spicy yogurt.

Serve.