Sicilian fish soup

Name: Sicilian fish soup
Ingredients: 1 red onion; 2 sticks celery; ½ small bulb fennel; 2 cloves garlic; 1 red chilli , deseeded; 2 tablespoons olive oil , plus extra for drizzling; 1 glass dry white wine; 800 g chopped plum tomatoes or passata; ½ butternut squash , peeled and grated; 500 ml organic fish stock; 200 g salmon fillet , from sustainable sources, ask your fishmonger, skinned; 300 g halibut fillet , from sustainable sources, ask your fishmonger, skinned; 12 raw peeled prawns or langoustine tails , from sustainable sources, ask your fishmonger; ½ lemon; 1 large handful fresh flat-leaf parsley , chopped