Thaw the puff pastry at room temperature for 40 minutes.
Preheat the oven to 375º Fahrenheit. Line a baking sheet with parchment paper.
In the bowl of a stand mixer (or in a regular bowl if using an electric mixer), add cream cheese, powdered sugar, vanilla extract, and salt. Mix until all the ingredients are well mixed and cream cheese is light and fluffy, about 2-3 minutes (scraping down the sides a few times).
Lay the pastry sheets flat on a clean, floured surface. Gently roll the sheets out to stretch slightly. Using a sharp knife or a pizza roller, cut each sheet into 9 squares.
Place the pastry squares on the prepared baking sheet. Evenly divide the guava slices among each square, leaving a ¼ inch border around the edges. Spread 2 tablespoons of the cream cheese mixture on top of the guava and cover with another pastry square. Gently press down the center and around the edges. Score the tops and transfer sheet pan to the freezer for about 10 minutes until pastries are well chilled (this will allow for the butter to melt slowly and pastries will hold their shape better).
Combine egg and water to form an egg wash and brush the tops with the egg wash. Sprinkle with coarse sugar (optional). Transfer to oven and bake for 15-18 minutes or until golden brown. Serve warm. Enjoy!
