If using frozen, store-bought puff pastry sheets, thaw them at room temperature according to package instructions.
Mix the softened cream cheese, vanilla extract, powdered sugar/icing sugar and strawberry jam in a small bowl until well combined.
Roll out the puff pastry sheet on a lightly floured work surface to about ¼ inch thickness.
Cut out as many hearts as possible from the puff pastry sheet using a heart-shaped cookie cutter. Place them on the prepared baking sheet. Make sure you place them an inch apart from each other.
Using a sharp knife, lightly score a heart inside each cut-out heart without cutting through the bottom of the dough. Instead of using a knife, you can use a smaller size heart cookie cutter in its place. Make sure you place the cookie cutter to make a heart mark. Do not cut the dough.
Spoon a teaspoon of the cream cheese and jam mixture onto the smaller heart/center of each puff pastry heart, leaving a border around the edges.
Add a few pieces of sliced strawberries on top of the cream cheese strawberry mixture.
Brush the edges of each pastry heart with the beaten egg. If you want to avoid eggs, use melted butter instead.
Repeat these steps with the entire batch of dough.
Preheat your oven to 375°F (190°C) and line a large baking sheet with parchment paper.
Bake in the oven for 12-14 minutes or until the pastry is puffed and golden brown.
Allow the pastry hearts to cool slightly before serving. Optionally, dust with fine sugar or granulated sugar before serving.