Asparagus Soup

1. Melt the butter, add chopped onion and fry gently for few minutes.
2. Add the chopped asparagus and cook for 3 minutes.
3. Add stock and bring to the boil. Reduce the heat and simmer for 20 minutes.
4. Remove from the heat and pour soup in a food processor.
5. Add cheese and process until smooth.
6. Reheat; season to taste with salt and pepper.
7. Serve garnished with sour cream and asparagus spears.