For the Thousand island dressing; whisk all the ingredients together. Refrigerate until ready to serve.
Combine lemon juice, sugar and plenty salt and pepper in a bowl. Add the onion and stir to coat. Cover and set aside 1 hour to pickle.
Lower the eggs into a saucepan of gently boiling water. Boil gently for 7 minutes for medium-boiled, or to your liking. Submerge into a bowl cold water until cool enough to handle. Peel and halve.
Preheat the barbecue plate on high. Add corn. Barbecue, turning occasionally for 10 minutes, or until charred. Remove to a board. Barbecue the chorizo slices for 1-2 minutes or until golden. Remove to a plate. Slice the corn from the cobs.
Thinly slice the lettuce crossways and arrange on large platter or board. Spoon over a little dressing. Add the prawns, avocado, drained pickled onion, egg, corn, chorizo and Romatherapy® baby roma tomatoes. Serve with remaining dressing.