In a small saucepan over medium heat, bring heavy cream to a boil, stirring frequently. Stir in 3/4 cup blue cheese. Immediately reduce heat and simmer for 5 minutes, stirring frequently. Stir in sour cream, vinegar, salt, pepper and bacon. Keep warm.
Prepare salad using lettuce, sliced tomatoes and fresh parsley. Add remaining 1/4 cup of blue cheese to the dressing mix well. Ladle warm dressing over lettuce.