01 - Preheat oven to 400°F (200°C) and line a baking tray with parchment paper.
02 - In a small bowl, combine cream cheese, granulated sugar, vanilla extract, and lemon zest. Blend until smooth and creamy. Set aside.
03 - In another bowl, toss diced strawberries with granulated sugar, lemon juice, and cornstarch. Mix to coat evenly and set aside.
04 - Unfold puff pastry sheet and roll gently if needed. Cut into 8 squares. Score a narrow border, about ⅜ inch, around the edges of each square without slicing through.
05 - Spread about 1 tablespoon of cream cheese mixture in the center of each pastry square, keeping inside the scored border. Top filling with 1 tablespoon of strawberry mixture.
06 - Combine beaten egg and milk in a small bowl. Brush pastry borders lightly with egg wash mixture.
07 - Bake pastries for 18 to 22 minutes or until puffed and golden brown. Remove from oven and transfer to a wire rack to cool slightly.
08 - For optional glaze, whisk together powdered sugar, milk, and vanilla extract until smooth. Drizzle glaze over cooled pastries before serving if desired.