Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

Unroll the thawed puff pastry sheets onto a lightly floured surface. You can gently roll them out a bit thinner if desired.

Cut each puff pastry sheet into 9-12 squares (approximately 3x3 inches each), or your desired size.

Place a slice or cube of guava paste in the center of half of the pastry squares, ensuring there is a border around the edges.

Brush the edges of the pastry squares with the guava paste with a little egg wash.

Place the remaining plain pastry squares on top of the ones with guava paste, aligning the edges. Gently press down around the edges to seal them. You can use a fork to crimp the edges for a decorative seal.

Transfer the sealed pastries to the prepared baking sheet.

Brush the tops of all the pastries generously with the remaining egg wash.

If desired, lightly sprinkle the tops of the pastries with granulated sugar before baking.

Bake for 20-25 minutes, or until the pastries are golden brown and puffed. Keep an eye on them to prevent over-browning.

Remove from the oven and let cool slightly on a wire rack. If using the optional simple syrup glaze (mix 1/2 cup sugar with 1/4 cup water, heat until dissolved), brush it over the warm pastries after baking for extra shine and sweetness. Serve warm or at room temperature.