Peel the garlic and press it through a garlic press. Mix mayonnaise, yoghurt and garlic and season with salt and pepper. Wash the dill, dab dry and chop finely.
Dill, except for something to sprinkle on top, mix into the sauce. Halve the avocados, peel them and remove the seeds. Cut avocado halves into pieces and mix with lemon juice. Mix the prawns and avocados with the sauce and season again with salt, pepper and possibly a little sugar.
Remove 8 beautiful leaves from the romaine lettuce, wash and dab dry. Use the rest of the lettuce for other purposes. Just before serving, place the lettuce leaves on a large plate and put some of the garlic shrimp in each leaf.
Sprinkle with the remaining dill.