Preheat oven to 400℉.
Mix soft cream cheese and sugar until smooth in a medium bowl. Stop the mixer. Scrape down the sides and bottom of the bowl. Add the egg yolk, lemon juice, and vanilla extract. Mix until smooth.
Unfold thawed puff pastry sheet. Cut into 6 equal pieces. Place rectangles on a parchment-lined baking sheet.
Spoon cream cheese filling onto the center of the puff pastry. Brush the edges of the puff pastry with the whisked egg. (This helps the edges to brown.)
Bake until the filling is set and the pastry is brown, about 18 minutes.
Store leftovers wrapped in the refrigerator for up to three days. Warm in a toaster oven or air fryer.
