Pastelitos de Crema (Cream Pastries)

In a saucepan, whisk together the eggs yolks, sugar, cornstarch, and salt. Gradually whisk in milk until smooth. Cook over medium heat, stirring constantly with a spatula, until mixture thickens and bubbles, about 5-7 minutes. Remove from heat and stir in butter and vanilla extract until smooth. Transfer to a bowl, cover with plastic wrap directly on the surface, and chill in fridge for at least 1 hour until completely cold.

Thaw puff pastry according to package instructions. On a lightly floured surface, roll each sheet into a 30x30 cm (12x12 inch) square. Cut each sheet into 9 equal squares (making 18 total). You'll use 12 squares as bottoms and 6 as tops (make extras if needed).

Preheat oven to 200°C (400°F). Line baking sheets with parchment paper. Place 1 heaping tablespoon of chilled cream filling in the center of 12 pastry squares. Brush edges of each square with egg wash. Top with remaining squares, pressing edges to seal. Use a fork to crimp edges for a decorative seal. Cut two small slits on top of each for steam vents. Brush tops with egg wash.

Bake for 18-22 minutes, until puffed and deep golden brown. Rotate pans halfway through for even browning. Transfer to a wire rack to cool for 10 minutes.

Dust cooled pastelitos generously with powdered sugar. Serve warm or at room temperature. These are best the day they're made but can be stored in an airtight container for up to 2 days.