Method

1. Remove tough stems and leaves from the broccoli. Cut off stalks, peel and cut them into 2.5cm/1inch pieces
2. Break the broccoli florets into small pieces and set them aside
3. Melt butter in a large saucepan
4. Add onion and broccoli stalks and cook, covered, for 5 minutes over a moderate heat, stirring frequently
5. Add reserved broccoli florets, potato and stock to pan
6. Bring mixture to boil
7. Cook, partially covered, for 5 minutes
8. Season to taste with salt and pepper and continue to cook over moderate heat for 20 minutes, or until vegetables are soft
9. Using a blender or food processor, puree mixture, then transfer to a clean saucepan
10. Add cream, lemon juice, Worcestershire sauce and Tabasco. Simmer for 3-5 minutes
11. Do not allow to boil or the soup will curdle
12. Just before serving, stir in the grated cheese and garnish each portion with watercress sprigs