01 - Preheat oven to 400°F. Line a baking tray with parchment paper.
02 - Combine softened cream cheese, granulated sugar, vanilla extract, and lemon zest in a small bowl. Mix until smooth and creamy. Set aside.
03 - In a separate bowl, toss diced strawberries with granulated sugar, lemon juice, and cornstarch. Set aside.
04 - Roll out the thawed puff pastry sheet and cut into 8 equal squares. Score a ½-inch border around each square, being careful not to cut all the way through.
05 - Place 1 tablespoon of cream cheese filling in the center of each pastry square. Gently spread within the scored border. Spoon 1 tablespoon of strawberry filling over the cream cheese layer.
06 - Beat egg with milk. Brush the outer pastry borders with the egg wash using a pastry brush.
07 - Transfer pastries to the prepared baking tray. Bake for 18 to 22 minutes, or until puffed and golden brown.
08 - Remove pastries from the oven and cool slightly on a wire rack.
09 - If desired, whisk powdered sugar, milk, and vanilla extract in a small bowl to form a smooth glaze. Drizzle over cooled pastries.