Cold prawn salad with creamy lemon dressing

Name: Cold prawn salad with creamy lemon dressing
Prep time: 20 min
Total time: 20 min
Cuisine: American
Ingredients: 300g sour cream; 1 cup (300g) whole-egg mayonnaise; 1 teaspoon finely grated lemon rind; 1½ tablespoons lemon juice; 3 green onions, chopped very finely; 3 baby cos lettuce; 600g cooked prawns, peeled; 3 small roma tomatoes, cut into wedges; ¼ cup (20g) fried Asian shallots; 2 tablespoons chopped fresh parsley; 2 green onions, finely chopped