In a small bowl, combine the soy sauce, miso and lemon zest and mix until smooth.

In a small saucepan, heat the sake and mirin over a high heat for 30 seconds to evaporate the alcohol. Then reduce the heat and whisk in the miso mixture until smooth. Increase the heat again and add the sugar, but be careful it doesn’t burn. Turn off the heat and leave to cool to room temperature.

Put the fish in a bowl. Smother both sides of each fillet generously with the cold miso mixture, then cover the bowl and refrigerate. Leave to marinate for at least 3 hours, or overnight, or up to 3 days, if you have the time.

When ready to cook, preheat the grill (broiler) to medium and preheat the oven to 150°C fan/170°C/340°F/gas mark 3. Wipe off any excess miso clinging to the fish.

Grill the fish, about 7.5 cm/3 in from the grill, skin side up first, for 3 minutes, until you see bubbles and a little charring.

Transfer to the oven and bake for 7–10 minutes until the fish is opaque and flakes easily. It will be just cooked and tender on the inside. Serve immediately with rice and simple steamed or stir-fried greens.