Place the prawns in a large bowl, add the oil and salt and toss well together so the prawns are lightly coated with the salt.
Make the aïoli. Place the egg yolks, vinegar, mustard, garlic cloves and a little salt and pepper in a food processor and blend briefly until the egg mixture is frothy. Then, with the blade running, gradually pour in the oil through the funnel until the sauce is thickened and glossy. Thin with a little boiling water if the sauce is too thick. Adjust the seasoning to taste.
Cook the prawns on a hot barbecue for 2—3 minutes on each side. Serve with the aïoli to dip the prawns into once they've been peeled, and a rocket salad.