First prepare all the ingredients. Take puff pastry out of the fridge only when you have everything ready (when it gets too warm it will be too hard to work with).
Preheat the oven to 400°F (200°C).
Make the cheese layer: in a medium bowl, whisk together cream cheese, powdered sugar, vanilla, lemon zest, and egg yolk until smooth.
2 ounces (60g) cream cheese, 2 tablespoons powdered sugar, 1 teaspoon vanilla extract, zest from 1/2 lemon, 1 egg yolk
Wash strawberries, dry with paper towels, and cut into small cubes.
1 cup (150g) strawberries
Make egg wash: whisk together the egg with 1 tablespoon of water.
1 egg
Take the puff pastry sheet out of the fridge and cut out hearts. They should be about 5 inches (12 cm) long. You can use heart-shaped cutters or cut them out by hand (this is what I did). See photos in the body of the post for reference.
1 puff pastry sheet
If at any point the dough becomes too soft and hard to work with, transfer it to a fridge for 5-10 minutes to allow it to harden.
Remove the scraps of the dough (you can use them to make cinnamon cookies, see notes). Transfer the pastry hearts to a baking sheet lined with parchment paper.
Score 1/2 inch (1 cm) border (don't cut all the way through), prick the middle of the tartlets with a fork.
Spoon the cheese filling in the middle of the tartlets, omitting the borders.
Place strawberries on top of the cheese filling.
Brush the borders of the pastries with the egg wash and sprinkle with granulated sugar.
1/2 tablespoon granulated sugar
Bake for 18-20 minutes or until golden brown.
Enjoy!