Pre-heat the oven to 200ºC/390ºF and line a baking sheet with baking paper.
Combine the strawberries and sugar and mix well. Allow to sit for 10 minutes for the strawberries to macerate and release their juices. Drain well.
Roll the puff pastry out onto a floured surface then using a heart-shaped cookie cutter (approximately 10cm/4 inches), cut out 16 hearts.
Place a teaspoon of Nutella followed by a teaspoon or two of the strawberry mixture onto the center of 8 pastry hearts. Brush around the edges with beaten egg then cover with another pastry heart.
Crimp edges with a fork then brush the tops with egg. Cut a few slits into the top of each heart then place onto the prepared baking sheet.
Place into the oven and allow to bake for 15-20 minutes or until the puff pastry is golden and cooked through.
Remove from the oven and allow to cool for 20 minutes before dusting with icing sugar (optional) and serving.