Portion the pineapple jam 1 tsp or 7-8 grams each.
Roll them into 1-inch/2.5 cm long cylinders with your hands. Set aside.
Pastry Dough
Mix the wet ingredients – In a large bowl, add butter and confectioners' sugar. Mix with a spatula or mixer just until combined. Add egg yolk and vanilla extract. Mix until combined.
Add the dry ingredients – Sift cake flour, cornstarch, milk powder, and salt into the wet ingredients. Mix until well incorporated.
Assemble
Preheat oven to 300F/150°C and line two baking pans with parchment paper or silicone mats.
Press the dough into strips – Place a small piece of dough into a Nastar mold. Press into a long strip with the pattern side down.
Encase the filling – Place one pineapple filling on the one end of the dough strip. Roll up the dough just enough to enclose the filling. Cut off the excess strip. Lightly press the ends of the dough together. Place the rolled pineapple tarts on the prepared baking sheets with the seam side down. Continue with the remaining dough and filling.
Bake for 18-20 minutes.
Cool slightly – Remove the cookies from the oven and let them cool on the pan for about 5-10 minutes.
Egg Wash
Make egg wash – While waiting for the cookies to cool, strain egg yolks into a small bowl to remove any lumps. Add a little bit of vegetable oil and mix until combined.
Brush the top of the cookies with the egg wash. Let the egg wash dry for about 10 minutes before brushing them again with the second coat of egg wash.
Bake at 300F/150°C for 10-15 minutes or until the top is golden brown.
Cool – Transfer nastar gulung to a cooling rack to cool completely. Store the cooled cookies in an airtight container.
Notes
Measuring by weight is recommended for this recipe.