Thaw puff pastry at room temperature for about 30 - 45 minutes while preheating your oven to 400°F (204°C). Line two large baking sheets with parchment paper.
Combine cleaned and sliced strawberries with sugar and cornstarch in a mixing bowl. Toss until well coated and let sit at room temperature for about 15 minutes.
Beat room temperature cream cheese until smooth, then blend in powdered sugar and vanilla extract until creamy and well-combined.
Unfold one sheet of puff pastry into a square and cut into six smaller rectangles. Score a border about ¼ inch from the edges of each rectangle without cutting all the way through.
Spoon one tablespoon of cream cheese filling into the center of each rectangle, layer fresh strawberries on top, brush edges with beaten egg, and sprinkle with sugar if desired.
Bake for about 20-25 minutes until light golden brown and flaky. Cool briefly before transferring to racks; top with warm strawberry jam or drizzle with a vanilla glaze.