Prawn and avocado cocktail

Method

1. Bring a pan of salty water to the boil. Cook the prawns until pink. Drain on kitchen paper, then cool in the fridge.
2. Meanwhile, whizz the egg yolk with the mustard and lemon juice in a food processor, then add the oil in a steady stream. The mayo is ready when the blades leave a trail in the mixture. Fold in the other flavourings by hand, and adjust to taste.
3. Remove the prawn shells, leaving the tail shell on for show, if you like.
4. Strip the lettuce and chicory down to their hearts (the tight, inner leaves) and finely shred. Peel, stone and cut the avocados into thin wedges. Lightly toss 1 tbsp of the dressing into the prawns, lettuce, chicory and avocados. Divide between glasses. Spoon the remaining dressing on top of the cocktails and sprinkle with a little cayenne pepper. Serve with lemon wedges.