Preheat oven to 400 degrees Fahrenheit and line two baking sheets with parchment paper.
In a medium bowl, beat 4 oz softened cream cheese, 3 tablespoons granulated sugar, and 1 egg yolk with an electric mixer until smooth.
Roll out 1 sheet puff pastry into a rough 12" by 12" square. Cut in half down the middle and cut each side into 4 pieces. Divide cream cheese mixture between 8 pieces of puff pastry and spread to within 1/2" of the outside.
With a fork, beat 1 egg white and 1 tablespoon water until combined. Brush around the exposed edges of the puff pastry.
Bake for 15 minutes or until golden brown. Remove from the oven and let cool 20-30 minutes.
Top with a layer of 1 pound thinly sliced strawberries and brush with 3 tablespoons warmed strawberry jam. Serve immediately.
Cover leftovers loosely with plastic wrap and serve within 6-8 hours.