Slice the cucumber in half lengthwise, remove the soft pulp and seeds and cut into 2-inch-(5-cm-) long matchsticks.

Cut the carrots into matchsticks of the same size.

Slice the ginger and gherkin into even finer strips and put them all into a bowl with the grated onion.

Sprinkle with 1 teaspoon of salt and set aside for 10 minutes.

Drain off the liquid.

Mix the sugar, vinegar and 1/2 cup of water together and pour the mixture into the bowl.

Let the vegetables marinate for 30 minutes.

Bring 10 cups of water to a boil in a poaching kettle.

Add 2 tablespoons of salt and 2 tablespoons of oil.

Place the fish carefully in the kettle.

When the water comes back to a boil, cover and turn off the heat.

Cook the fish in this way in the water for 30 minutes.

Meanwhile, drain the vegetables, reserving the marinade.

In a small bowl combine the marinade and the hoisin sauce.

Mix the cornstarch with a tablespoon of cold water and stir it into the marinade mixture.

Heat the teaspoon of oil in a small saucepan.

Add the garlic and fry for 1 minute.

Add the marinade mixture and simmer, stirring, for 2 to 3 minutes.

Gently lift the fish onto a serving dish, sprinkle with salt and pepper, cover with the marinated vegetables and spoon the sauce over the top.

Serve immediately.