Heat 60ml heavy cream in a small glass bowl or measuring cup (in the microwave) or small saucepan (on the stovetop) to about 110°F. Squeeze the excess water from the gelatin and whisk it into the heated cream until fully melted and incorporated - set aside to cool.
60 ml heavy cream
In a medium mixing bowl, Whisk together the mascarpone cheese, powdered sugar, lemon juice, lemon zest, salt and vanilla.
226 g mascarpone cheese, 60 g powdered sugar, 1 lemon, 1 pinch salt, 5 ml vanilla
Slowly whisk the cooled gelatin and cream mixture into the mascarpone mixture.
Continue whisking while slowly streaming in the remainder of the cold heavy cream.
180 ml heavy cream
Switch to an electric mixer and beat until medium peaks form. Transfer to a large piping bag and refrigerate for at least one hour or until ready to use. (Yield: about 3½ cups)[You can continue to whisk by hand, but it will take longer and give you quite the arm workout]