Cheesy Potato and Cauliflower Soup

Melt the butter in a large pot over medium heat. Add onions and saute until tender. Meanwhile, place the broccoli and cauliflower into a large pot with 1.5 litres water. Bring to the boil and cook until fork tender, but broccoli is still a vibrant green. Drain and reserve 1.25 litres of the water.

Pour the reserved water into the pot with the onions. Bring to the boil and add potatoes, spinach and stock cubes. Cook for about 15 minutes, until potatoes are tender. Remove half of the soup and puree in small batches using a food processor or liquidiser. Return to the pot and stir in the broccoli, cauliflower and Cheddar cheese. Stir until cheese is melted; serve immediately.