Step 1

Place butter on a 9x13-inch sheet of parchment paper and top with another sheet of parchment. Roll or press butter into a rectangle about 12 by 6 inches. Place parchment-covered butter on rimmed baking sheet and refrigerate until cold, about 1 hour.

Step 2

Meanwhile, stir flour, salt, and water in a medium bowl until it forms a smooth ball, or mix in stand mixer fitted with a dough hook. Add a few drops of water to bring the dough together if needed, or a dusting of flour if dough is too sticky; it will vary depending on the humidity among other factors. Cover bowl and let dough rest for 15 minutes.

Step 3

Roll dough into a 12x6-inch rectangle on a lightly floured work surface. Remove parchment paper from butter and arrange butter in center of dough so the short side of the butter meets the edges of the short side of the dough. Fold flaps of dough over butter; pinch edges or smack with a rolling pin to seal butter completely. Gently roll dough lengthwise to 12 inches long. Fold dough into thirds, wrap in plastic, and refrigerate. Repeat process of rolling, folding, and refrigerating 5 more times, rolling out dough smooth-side up. Refrigerate 30 minutes.

Step 4

Roll dough to a 12x12-inch rectangle, trimming edges if needed. Cut into 4 strips, each measuring about 3 inches across. Cut each strip crosswise into 4 equal pieces to make sixteen 3x3-inch squares. Refrigerate dough squares until ready to use. Brush edges of 8 squares with egg wash. Place 1 tablespoon cream cheese and 1 tablespoon guava paste in center of each square. Top with remaining pastry squares and press edges together. Using tines of a fork, press edges firmly to seal. (If fork sticks to pastry, dip tines in flour.) Using a small sharp knife, cut an X on top of each pastry. Place on a parchment paper-lined baking sheet, spacing evenly apart, cover, and refrigerate until ready to bake. Cover and refrigerate egg wash.

Step 5

Preheat oven to 400°F. Brush pastries with egg wash and sprinkle with granulated sugar, if using. Bake pastries until puffed, crispy, and golden brown, about 25 minutes, rotating baking sheet halfway through. Let cool about 30 minutes before eating.