Mash cheese with parsely into coarse paste in medium bowl with fork. Whisk olive oil and 2 tablespoons of the lemon juice in small bowl; stir into cheese mixture. Season to taste with salt and pepper.
Cut avocados lengthwise in half; remove pits. Scoop two thirds of the flesh out of each avocado half, leaving a thin shell, and add to cheese mixture; mix well. Taste and adjust seasoning.
Sprinkle insides of avocado shells with remaining lemon juice; place on serving plate lined with lettuce leaves. Spoon cheese mixture into avocado shells, dividing evenly.
Garnish with olives.