Fish and potato chowder

Ingredients

• 1 teaspoon olive oil
• 1 onion, finely chopped
• 2 sticks celery, finely chopped
• 500ml reduced-salt fish or vegetable stock
• 300ml skimmed milk
• 200g baby new potatoes, halved
• 100g skinless smoked haddock, diced
• 200g skinless white fish, eg. cod or pollack, diced
• 198g can salt-free sweetcorn
• 2 tablespoons low-fat creme fraiche
• 2 tablespoons fresh chives, finely chopped
• Freshly ground black pepper