In a bowl of a stand mixer or in a bowl with a hand mixer, beat the mascarpone with the 6 ½ tablespoons of powdered sugar, until smooth. Mix in the lemon curd.
Scrape the mixture into a medium bowl. Set aside. Clean and dry the mixing bowl and attachment.
Whip the heavy cream until lines begin to appear. Add the 1 tablespoon of powdered sugar and continue whipping until fluffy.
Fold the whipped cream into the cheese mixture, reserving 1/2 cup of whipped cream for piping on top of tart, if desired.
Spread the mascarpone/cream mixture over the tart shell. Decorate by piping stars of whipped cream. Add 1/2 pint washed and dried blueberries, blackberries, or raspberries, herbs, lemon slices, or washed and dried edible flowers.
Cover tart or mini tarts with cellophane. Chill for 3-4 hours in the refrigerator. Or freeze for 1-2 hours. Remove from freezer 30-45 minutes before enjoying. Remove springform bottom after freezing or chilling.