For the crust chop the pistachios coarsely. Mix pistachios, mustard and breadcrumbs well in a bowl. Season with salt and pepper. Wash the tomatoes, grate them dry and halve or quarter them. Peel onion and cut into rings. Wash basil, shake dry and remove leaves. Season vinegar with salt and pepper, stir in oil
Wash the fish and dab dry. Bring the broth to a boil in a pot. Add the fish and let it simmer in a closed saucepan in lightly boiling broth for about 3 minutes. Remove and place on a baking tray lined with baking paper. Keep fish stock warm. Spread the pistachio crust on the fish.
Bake under the preheated oven grill for about 5 minutes. Arrange tomatoes, onion and basil on a plate, drizzle with vinaigrette. Wash the chives, shake dry and cut diagonally into small rolls. Remove the fish and season with salt, pepper and lemon juice. Sprinkle with chives. Add to the tomato salad and sprinkle with 2 tablespoons of fish stock