Wash the potatoes and cook in boiling water for 25-30 minutes. In the meantime, wash the fish fillet, dab dry and cut into 12 longish pieces. Sprinkle with lemon juice, salt lightly and put aside.
Wash the basil and parsley, dab dry and chop coarsely, except for a little to garnish. Peel the garlic. Finely chop the herbs, garlic, pine nuts and Parmesan cheese in the universal chopper.
Mix in olive oil and season with salt and pepper. Clean and wash the zucchini and cut them lengthwise into wafer-thin slices with a wide peeler. Spread fish with pesto on both sides.
Wrap 2 zucchini slices around a strip of fish and pin them with a wooden skewer. Drain the potatoes and cut in half. Brush the cut surfaces of the hot potatoes with butter.
Place a piece of solid aluminium foil on one half of the grill rack. Brush with oil. Place fish rolls on top and cook on the hot grill for 12-15 minutes. Turn over in between. Place potato halves and possibly some lemon pieces on the grill 5 minutes before the end of the cooking time.
Sprinkle baked potatoes with coarse sea salt and serve with the fish rolls. A rocket salad tastes good with it.