Melon with Prawns and Strawberries

Description
Cook's notes: when melons are ripe they should "give" slightly when pressed at the stalk end. wrap up Melons well if storing them in the refrigerator as otherwise they will permeate everything around them with their heady scent.
 * Preparation time: 20 minutes
 * Freezing: not recommended

Ingredients

 * ½ medium-size avocado
 * ½ tsp lemon juice
 * 1 medium-size, ripe seasonal melon (i.e. ogen, cantaloupe or honeydew)
 * 1 celery heart, chopped
 * 4 oz strawberries, hulled and sliced
 * 8 oz cooked, peeled prawns (thawed if frozen)
 * 2 little gem lettuces, rinsed and torn into pieces

Dressing

 * 8 oz strawberries
 * 1 tsp caster sugar
 * 2 tsp olive oil
 * 1 tbsp unsweetened orange juice
 * 2 tsp chopped fresh parsley
 * salt and freshly ground black pepper

Directions

 * 1) Peel and chop the avocado and place it in a mixing bowl.
 * 2) Sprinkle it with the lemon juice to prevent it from discolouring.
 * 3) Halve the melon, discard the seeds and scoop out the flesh using a melon baller (or cut it into cubes).
 * 4) Gently combine the melon, chopped celery, strawberries and prawns with the avocado and refrigerate until needed.
 * 5) Meanwhile, purée the dressing ingredients in a food processor or liquidiser.
 * 6) Arrange the lettuce on 4 plates and divide the prawn mixture between them.
 * 7) Pour the dressing over and serve immediately.