Step 1
In a medium saucepan, place the guavas and water and bring to a boil. Reduce heat to simmer and cook the guavas until very tender, about 10 minutes. Remove from heat. Place guavas and water in a blender or food processor and process. Strain the pulp and discard the seeds.
Step 2
Return the pulp to the saucepan and cook with brown sugar, lemon juice, cinnamon stick, and salt over medium heat. Stir constantly with a wooden spoon until the mixture is thick. Remove from heat and cool completely.
Step 3
Preheat oven to 400°F. Line two baking sheets with parchment paper.
Step 4
Over a slightly floured surface, roll each sheet of puff pastry to a 12x12-inch square. Cut the sheets into 9 smaller squares. You will have 18 squares total.
Step 5
Prepare an egg wash by whisking together 1 egg and 1 teaspoon of water. Brush the edges of each square with egg wash. Add 2 teaspoons of guava jam to the center of each square. Fold the pastry diagonally over the guava jam and seal each pastry by pressing with a fork.
Step 6
Transfer pastries to prepared baking sheets and brush each pastry with egg wash. Sprinkle with granulated sugar. With a sharp knife, make a small slit on top of each pastry. Bake for 15 minutes or until golden brown. Serve warm.