Defrost the prawns if necessary. Peel the grapefruit so that the white skin is completely removed. Remove the fillets with a sharp knife between the parting skins. Squeeze the juice out of the parting skins and collect it.
Clean the chilli, cut lengthwise, remove seeds, wash and cut into thin rings. Mix grapefruit juice, vinegar, chili, salt, pepper and 1 pinch of sugar. Fold in 3 tablespoons of oil.
Sort the salad, wash and drain. Cut the avocados in half lengthwise and remove the stone. Remove the flesh from the peel and cut into pieces. Mix with the grapefruit fillets, olives and vinaigrette.
Peel and finely chop the garlic. Shrimps, possibly up to the tail fins, peel. Cut lengthwise on the back, remove the dark intestine. Wash shrimps and dab dry. Heat 1 tbsp. oil in a frying pan.
Fry the prawns for 3-4 minutes while turning. Add garlic and fry briefly. Season with salt and pepper.
Fold the salad into the avocado-grapefruit mix. Arrange everything and sprinkle with coarse pepper.