Peel, wash and possibly halve the potatoes. Cook in boiling salted water with 1 teaspoon broth powder for about 20 minutes.
In the meantime wash and clean the cucumber, cut it in half lengthwise and slice it. Wash and halve the tomatoes. Mix 2 tablespoons pesto, salad cream and 2 tablespoons vinegar. Wash fish, dab dry and marinate with salt, sugar and lemon juice.
Heat the oil in a large frying pan and fry the fish for about 5 minutes while turning.
Drain the potatoes and collect approx. 4 tbsp. of cooking liquid. Marinate potatoes with 4 tablespoons of vinegar. Mix vegetables, pesto cream, cooking liquid and potatoes, season with salt and pepper. Arrange potato salad and fish, drizzle with remaining pesto and garnish with basil.