Potato and leek soup

Ingredients

• 1 tablespoon olive oil
• 50 grams butter
• 4 potatoes (800g), chopped coarsely
• 1 leek (500g), sliced thickly
• 300 millilitres cream
• 2 tablespoons finely chopped fresh chives
• 1 tablespoon finely chopped fresh basil
• 1 tablespoon finely chopped fresh dill
• Vegetable broth
• 2 potatoes (400g), chopped coarsely
• 2 carrots (240g), chopped coarsely
• 1 brown onion (200g), chopped coarsely
• 1 tomato (150g), chopped coarsely
• 1 stalk celery (150g), trimmed, chopped coarsely
• 1 1/2 litres (6 cups) water