Halve the avocados then remove the stones. Drizzle wit lemon juice and season with salt and pepper.
Bring a pot of water to a simmer then add the lemon rind, peppercorns and a tablespoon of salt. Fill a large bowl with water and ice.
Poach the prawns/shrimp in the simmering water until the prawns turn pink/opaque. Remove the prawns with a slotted spoon and immediately plunge into the ice water to stop them from cooking further.
Drain the prawns well.
To make the sauce, combine the mayonnaise, tomato paste, ketchup, Worcestershire sauce, lemon juice and hot sauce in a bowl and mix well. Season with salt and pepper.
Pour the sauce over the poached prawns/shrimp and mix well.
Spoon a generous amount of the prawn cocktail onto each avocado and sprinkle with chopped chives.