Add the quark, tomato puree, white wine vinegar, Henderson’s relish (or Worcestershire sauce), paprika, and gherkins to a bowl, and mix. Season to taste with pepper, then squeeze in the juice from one of the lemon wedges.
Add the prawns to the sauce, and mix to coat. Arrange the salad leaves on a plate or in a bowl.
Arrange the prawns on each lettuce leaf and add the cucumber, cherry tomatoes, and lemon wedges.