Vegetable stock

• 2 white onions, quartered
• 1 leek, quartered
• 3 celery sticks, halved

Place everything in a large pot with 4 litres of water and bring to a boil. Turn down the heat and simmer for 1 hour. Carefully strain the stock through a fine sieve into a bowl and leave to cool. Store in the fridge for up to 4 days.