Mix mayo and ketchup together.
Finish by seasoning with the rest of the ingredients. Refrigerate.
Make a lemon vinaigrette by mixing the lemon juice and olive oil together in a bottle and shaking vigorously.
De-vein the prawns and remove the heads. Set aside for prawn oil.
Blanch prawns tails (shell on), in salted boiling water for 2 minutes.
Shock in ice water immediately.
Peel the prawns, keeping the tail in-tact. Refrigerate for later.
Cut the witlof in half and remove the cores with a reverse 'V' cut.
Blanch for 30 seconds in salted boiling water and ice immediately.
Once cool, drain the witlof well and place in a boil and season with oil and a pinch of salt.
Char in a hot pan with oil and them cool down completely.
Shave the fennel really thin using a mandolin and place in lemon water to prevent oxidation.
To plate, place a spoon of Marie Rose on the plate and spread using the back of a spoon in a circular motion.
Season shaved fennel with lemon vinaigrette and salt. Place charred witlof halves and shaved fennel around the plate. Spread 5 prawns around the plate, ensuring everything is plated within the circular outline of the emulsion.