Stir in parsley, cream cheese, lemon juice and Worcestershire sauce. Season to taste with salt and pepper. Add blue cheese. Mix until well combined. Spoon cheese mixture into mushroom caps, filling generously.
Place caps on cookie sheet.
Bake at 425 F 8 - 10 minutes. 50 mL Remove stems from mushrooms. Coarsely chop stems. In large frypan, over medium-high heat, cook onion and beef until lightly browned and no pink remains in beef. Add mushrooms stems, ham and sherry.