In a large bowl, add the cream cheese and powdered sugar and blend with with a hand mixer on medium-high speed until creamy.
Add the lemon juice, and lemon extract (if using) and stir gently with a rubber spatula just until combined. Then stir in the whipped topping.
Add the blueberries and marshmallows and stir gently to just coat them with the cream cheese mixture.
Cover with plastic wrap and place in the refrigerator to chill for 30 minutes to an hour for the flavors to meld and the marshmallows to soften.
Garnish with additional fresh blueberries, lemon slices, and/or mint leaves if desired.
