Sort the rocket, wash it, dab it very dry and chop it. Wash the lemons. Finely grate the zest of 1 lemon and squeeze the juice. Peel the garlic and press it through the garlic press.
Mix butter, garlic, chopped rocket, 1 tablespoon lemon juice and zest, season with salt and pepper and place on baking paper. Form a roll (approx. 10 cm long) with the paper and form a triangular roll by pressing the sides together.
Cold. Wash potatoes thoroughly and cook in salted water for about 20 minutes. Drain, let cool a little and cut lengthwise. Spread with 1 tablespoon of olive oil, cover with sage and sprinkle with a little coarse salt.
Wrap the potatoes individually in foil. Before serving, warm them up on the grill for 15 minutes at medium heat. Wash the fish and pat dry. Sprinkle with remaining lemon juice and oil and salt.
Grill on the grill for 1-2 minutes from both sides. Cut remaining lemon into corners and grill briefly. Cut butter into slices and serve with fish. Serve with rocket tomato salad.