Creamy Potato Soup

• 5 sprigs parsley tied
• 4 waxy boiling potatoes
• 3 ribs celery
• 2 onions
• 1 leek
• 1 bay leaf
• 1,400 ml chicken broth
• 180 ml cream (heavy)
• 34 gr butter (unsalted)
• 5 ml worchestershire sauce