Corn soup with avocado cream

Name: Corn soup with avocado cream
Ingredients: 35g butter; 1 large onion, finely chopped; 1 stick celery, diced; 100g potatoes, peeled and diced; 1 leek, coarse outer leaves removed, base and top trimmed; ½tsp cayenne pepper (or ¼tsp if you prefer less heat); 500g fresh or frozen sweetcorn kernels; 1 litre vegetable or light chicken stock; 30ml double cream; 2-3 limes, juice; 2 large ripe avocados; 2tbsp white balsamic vinegar; 2½tbsp extra virgin olive oil (use a fruity variety rather than a grassy one); 2-3 limes, juice; 3tbsp coriander leaves; 5tbsp single cream; 2-3 red chillies, finely shredded; Coriander leaves