Preheat your oven to 200°C (400°F)
In a bowl, mix together the mascarpone cheese, 50g (¼ cup) powdered sugar, and 1 tsp vanilla extract until well combined.
Cut the puff pastry into 4x4 or 4.5x4 inch squares.
Place a dollop of the mascarpone mixture in the center of each pastry square, leaving a border around the edges.
Add about a teaspoon of lemon curd on top of the mascarpone mixture.
Fold the pastry over the filling, crimping the edges with a fork to seal.
Brush the tops of the danishes with the beaten egg.
Bake for 15-20 minutes or until the pastry is puffed up and golden brown.
Transfer the danishes to a wire rack and let cool.
Dust with powdered sugar, if desired.
