In a medium heavy-bottomed saucepan, combine the mirin and sake and bring to a boil. Boil for 1 minute (to cook off the alcohol), reduce the heat to medium, add the miso, and stir until dissolved. Add the sugar, increase the heat, and stir until the sugar is dissolved, about 5 minutes.Remove from the heat and cool to room temperature.

Dry the fillets with paper towels and put them in a gallon-size sealable plastic bag. Add the miso glaze, seal and refrigerate for 24 to 48 hours.

Bring the fillets to room temperature. Preheat the broiler or place a grill pan or heavy skillet over high heat. Wipe excess glaze from the fillets and broil or grill, turning once, until brown and glazed, about 8 minutes. Transfer to plates and serve.

Tips

This also makes an elegant starter. Just reduce the portion size by half and serve the cod on greens lightly dressed with Asian Vinaigrette. I also use this glaze brushed on eggplant when I grill it. Serve the eggplant with roasted meat.