Use a mixture of king prawns and smaller prawns for the maximum texture and taste in this classic starter.
Place all of the dressing ingredients into a food processor and blend until combined and smooth, then season to taste with salt and freshly ground black pepper. Place into a bowl and store in the fridge until ready to serve.
To make the prawn cocktail, place the prawns and dressing into a bowl and mix together gently.
Tear the grapefruit segments into chunks and add them to the prawn mixture, stirring to combine.
Place the cabbage, fennel and lettuce into a separate large bowl and mix together well.
Divide the salad mixture among eight flat sundae glasses or bowls.
Spoon equal portions of the prawn and grapefruit mixture over the top of each.
Garnish with a slice of lime, a few coriander leaves and a few shreds of red chilli and serve.