Preheat your oven to 200ºC ( 400°F) and line a baking tray with baking paper.
Roll out the puff pastry sheet on a lightly floured surface.
With a pizza cutter or a sharp knife , cut the puff pastry sheet into 12 strips (about 1 inch wide ).
Lightly grease the cream horn molds and gently wrap each strip of puff pastry around them, starting at the pointy tip and overlapping slightly as you go. Gently press the end of the dough strip into the dough next to it.
Repeat with all the strips. Place all the wrapped molds on the prepared baking sheet and bake in the preheated oven for 15-20 minutes or until golden and puffy.
Let them cool completely and , then carefully remove the molds.
In the mean time, prepare mascarpone whipped cream. In a large mixing bowl combine heavy cream, mascarpone, sugar and vanilla extract and and whip with a hand mixer until stiff peaks form.
Adjust sweetness and fill in a piping bag. Store in the fridge until ready to serve.
When ready to serve ,fill the cooled cream horns with mascarpone whipped cream.
Dust with icing sugar before serving , if desired.
Enjoy!